diff --git a/checkin_notes b/checkin_notes
index 198b58b2a3..17b9bdf736 100644
--- a/checkin_notes
+++ b/checkin_notes
@@ -6047,3 +6047,19 @@ David  22 Sept 2012
         cs_statefile.cpp
         script/
             boinc-client.in
+
+David  23 Sept 2012
+    - web: add global prefs reset button
+    - change default disk prefs to:
+        - no absolute limit on disk usage (we need to work with future disks)
+        - keep 100 MB min free space
+        - use up to 90% of total space
+
+    html/
+        user/
+            prefs_default.php (new)
+            prefs.php
+        inc/
+            prefs.inc
+    lib/
+        prefs.cpp
diff --git a/html/inc/prefs.inc b/html/inc/prefs.inc
index a3ba79ece5..74c295bf2c 100644
--- a/html/inc/prefs.inc
+++ b/html/inc/prefs.inc
@@ -408,9 +408,9 @@ function get_disk_space_config() {
     $dp->disk_max_used_pct = parse_config($config, "<default_disk_max_used_pct>");
     $dp->disk_min_free_gb = parse_config($config, "<default_disk_min_free_gb>");
     // set some defaults if not found
-    if (!$dp->disk_max_used_gb) $dp->disk_max_used_gb = 100;  // 100 gb
-    if (!$dp->disk_max_used_pct) $dp->disk_max_used_pct = 50; // 50 percent
-    if (!$dp->disk_min_free_gb) $dp->disk_min_free_gb=.001;   // 1 megabyte
+    if (!$dp->disk_max_used_gb) $dp->disk_max_used_gb = 0;  // no limit
+    if (!$dp->disk_max_used_pct) $dp->disk_max_used_pct = 90; // 90 percent
+    if (!$dp->disk_min_free_gb) $dp->disk_min_free_gb=.1;   // 100 MB
     // set mininimum free space scheduler allows 
     // - depends on which scheduler is running
     $dp->new_sched_flag = 1;
@@ -584,7 +584,7 @@ function default_prefs_project() {
     global $project_pref_descs;
 
     $p = null;
-    foreach($project_pref_descs as $pref) {
+    foreach ($project_pref_descs as $pref) {
         $pref->set_default($p);
     }
     $p->project_specific = project_specific_prefs_default();
@@ -814,7 +814,10 @@ function prefs_display_venue($prefs, $venue, $subset) {
             prefs_show_project($x);
             prefs_show_project_specific($x);
         }
-        row2("<br>", "<a href=prefs_edit.php?venue=$venue&subset=$subset$tokens>".tra("Edit preferences")."</a> | <a href=prefs_remove.php?venue=$venue&subset=$subset$tokens>".tra("Remove")."</a>");
+        row2("<br>",
+            "<a href=prefs_edit.php?venue=$venue&subset=$subset$tokens>".tra("Edit preferences")."</a>
+            | <a href=prefs_remove.php?venue=$venue&subset=$subset$tokens>".tra("Remove")."</a>
+        ");
         end_table();
         echo "</td></tr>\n";
     } else {
@@ -889,7 +892,9 @@ function print_prefs_display_global($user, $columns=false) {
         start_table();
         prefs_show_global($global_prefs);
         $tokens = url_tokens($user->authenticator);
-        row2("<br>", "<a href=prefs_edit.php?subset=global$tokens>".tra("Edit preferences")."</a>");
+        row2("<br>",
+            "<a href=prefs_edit.php?subset=global$tokens>".tra("Edit preferences")."</a>
+        ");
         end_table();
         echo "</td></tr>\n";
 
@@ -1170,12 +1175,10 @@ function global_prefs_update(&$user, $prefs) {
     $query = "update user set global_prefs='$prefs_xml' where id=$user->id";
     $retval = mysql_query($query);
     if (!$retval) {
-        echo tra("Update failed: ").htmlspecialchars($query)."\n";
-        echo mysql_error();
-        exit();
+        return 1;
     }
     $user->global_prefs = $prefs_xml;
-    return $retval;
+    return 0;
 }
 
 function project_prefs_update(&$user, $prefs) {
@@ -1184,8 +1187,11 @@ function project_prefs_update(&$user, $prefs) {
     $show_hosts = $user->show_hosts?1:0;
     $query = "update user set project_prefs='$prefs_xml', send_email=$send_email, show_hosts=$show_hosts where id=$user->id";
     $retval = mysql_query($query);
+    if (!$retval) {
+        return 1;
+    }
     $user->project_prefs = $prefs_xml;
-    return $retval;
+    return 0;
 }
 
 ?>
diff --git a/html/user/prefs.php b/html/user/prefs.php
index bd055e6d0a..f94017d1b7 100644
--- a/html/user/prefs.php
+++ b/html/user/prefs.php
@@ -20,8 +20,6 @@ require_once("../inc/db.inc");
 require_once("../inc/util.inc");
 require_once("../inc/prefs.inc");
 
-check_get_args(array("subset", "cols", "updated"));
-
 db_init();
 
 $user = get_logged_in_user();
@@ -29,6 +27,7 @@ $user = get_logged_in_user();
 $subset = get_str("subset");
 $columns = get_int("cols", true);
 $updated = get_int("updated", true);
+$defaults = get_int("defaults", true);
 
 page_head(tra("%1 preferences", subset_name($subset)));
 if (isset($updated)) {
@@ -40,11 +39,28 @@ if (isset($updated)) {
         </p>
     ";
 }
+if (isset($defaults)) {
+    echo "<p style='color: red'>
+        ".tra("Your preferences have been reset to the defaults, and
+          will take effect when your computer communicates with %1
+          or you issue the %2Update%3 command from the BOINC Manager.",
+          PROJECT, "<strong>", "</strong>")."
+        </p>
+    ";
+}
 if ($subset == "global") {
     print_prefs_display_global($user, $columns);
+    if (!$defaults) {
+        show_button(
+            "prefs_default.php",
+            "Restore defaults",
+            "Restore default preferences"
+        );
+    }
 } else {
     print_prefs_display_project($user, $columns);
 }
+
 page_tail();
 
 $cvs_version_tracker[]="\$Id$";  //Generated automatically - do not edit
diff --git a/html/user/prefs_default.php b/html/user/prefs_default.php
new file mode 100644
index 0000000000..5cdf8a62b7
--- /dev/null
+++ b/html/user/prefs_default.php
@@ -0,0 +1,49 @@
+<?php
+// This file is part of BOINC.
+// http://boinc.berkeley.edu
+// Copyright (C) 2012 University of California
+//
+// BOINC is free software; you can redistribute it and/or modify it
+// under the terms of the GNU Lesser General Public License
+// as published by the Free Software Foundation,
+// either version 3 of the License, or (at your option) any later version.
+//
+// BOINC is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+// See the GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with BOINC.  If not, see <http://www.gnu.org/licenses/>.
+
+// reset user's preferences to the defaults
+
+require_once("../inc/util.inc");
+require_once("../inc/prefs.inc");
+
+$confirmed = get_int("confirmed", true);
+$user = get_logged_in_user();
+
+if (!$confirmed) {
+    page_head("Confirm reset preferences");
+    echo "
+        You have requested restoring your computing preferences
+        to the default settings.
+        Your current preferences will be discarded.
+        Do you really want to do this?
+        <br>
+    ";
+    show_button("prefs_default.php?confirmed=1", "Yes", "Restore default preferences");
+    show_button("prefs.php", "No", "Keep current preferences");
+    page_tail();
+} else {
+    $prefs = default_prefs_global();
+    $retval = global_prefs_update($user, $prefs);
+    if ($retval) {
+        error_page("Couldn't restore default preferences.");
+    } else {
+        Header("Location: prefs.php?subset=global&defaults=1$c");
+    }
+}
+
+?>
diff --git a/lib/prefs.cpp b/lib/prefs.cpp
index 5d232e3d22..d383945fea 100644
--- a/lib/prefs.cpp
+++ b/lib/prefs.cpp
@@ -225,8 +225,8 @@ void GLOBAL_PREFS::defaults() {
     max_ncpus = 0;
     cpu_scheduling_period_minutes = 60;
     disk_interval = 60;
-    disk_max_used_gb = 10;
-    disk_max_used_pct = 50;
+    disk_max_used_gb = 0;
+    disk_max_used_pct = 90;
     disk_min_free_gb = 0.1;
     vm_max_used_frac = 0.75;
     ram_max_used_busy_frac = 0.5;