Best suggestion I can offer is to download Process Explorer[^] and see which process is using all the CPU time. If you post which process that is, maybe we can help. Windows XP has a flaw in Explorer where, if you right-click a file that isn't selected, and the Task Pane has to adjust its size, a thread goes into an infinite loop and uses 100% of one processor (or physical or logical core on dual-core or hyperthreading processors). This condition goes away once you dismiss the context menu. If the process is a svchost.exe process, or 'System' (which isn't a true processes), then double-click it, and go to the Threads tab. This will show the threads running in the process - make a note of the one that's using the CPU time. For best results, download and install the Debugging Tools for Windows[^], set the _NT_SYMBOL_PATH environment variable for access to the Microsoft Symbol Server (see here[^] for how to do this), and point Process Explorer to the Debugging Tools version of dbghelp.dll via Options, Configure Symbols.
Stability. What an interesting concept. -- Chris Maunder