Index: perfdata.c
===================================================================
--- perfdata.c	(revision 39746)
+++ perfdata.c	(working copy)
@@ -134,36 +134,54 @@
     }
 
     /* Get handle information
+     * Support 2 interfaces:
+     * If the call does not succeed it returns the required size (new)
+     * - or -
      * We don't know how much data there is so just keep
-     * increasing the buffer size until the call succeeds
+     * increasing the buffer size until the call succeeds (old)
      */
-    BufferSize = 0;
+    BufferSize = 0x10000;
     do
     {
-        BufferSize += 0x10000;
         SysHandleInfoData = (LPBYTE)HeapAlloc(GetProcessHeap(), 0, BufferSize);
 
         status = NtQuerySystemInformation(SystemHandleInformation, SysHandleInfoData, BufferSize, &ulSize);
 
         if (status == STATUS_INFO_LENGTH_MISMATCH) {
+            if(ulSize <= BufferSize) {
+                //Old NT4 (?) interface
+                BufferSize += 0x10000;
+            } else {
+                //New XP interface
+                BufferSize = ulSize;
+            }
             HeapFree(GetProcessHeap(), 0, SysHandleInfoData);
         }
 
     } while (status == STATUS_INFO_LENGTH_MISMATCH);
 
     /* Get process information
+     * Support 2 interfaces:
+     * If the call does not succeed it returns the required size (new)
+     * - or -
      * We don't know how much data there is so just keep
-     * increasing the buffer size until the call succeeds
+     * increasing the buffer size until the call succeeds (old)
      */
-    BufferSize = 0;
+    BufferSize = 0x10000;
     do
     {
-        BufferSize += 0x10000;
         pBuffer = (LPBYTE)HeapAlloc(GetProcessHeap(), 0, BufferSize);
 
         status = NtQuerySystemInformation(SystemProcessInformation, pBuffer, BufferSize, &ulSize);
 
         if (status == STATUS_INFO_LENGTH_MISMATCH) {
+            if(ulSize <= BufferSize) {
+                //Old NT4 (?) interface
+                BufferSize += 0x10000;
+            } else {
+                //New XP interface
+                BufferSize = ulSize;
+            }
             HeapFree(GetProcessHeap(), 0, pBuffer);
         }