|Try going into task manager, and selecting File > New Task (Run...) and typing in "explorer.exe" - if that does not work, you can also try running Windows File Protection. Get to the "Run" menu from Task Manager the same way, but this time type in "sfc /scannow" - this will initiate the System File Checker and make sure all system files are intact and good. If there is a problem detected it will make use of the system file cache on your computer. If it still cannot fix the problem, you will be asked to insert your Windows XP Install CD. Please post an update when you get a chance.|
Also: "wuauclt.exe" is technically a program for receiving critical Windows updates, but, I've heard more than once that there are a couple of viruses that will use that program name as a disguise. When you do fix your "explorer.exe" problem, I would suggest turning off your automatic updates and then checking to see if "wuauclt.exe" is still running. If it is, more likely than not you have a trojan/virus infection. Hope this helps!