explorer.exe seems to be corrupt, this happened to a friend's laptop that I had to fix. The only thing i could do was reinstall windows xp, so you might have to do that or a repair install. If you have things on there you would like to back up you can still back them up using task manager.
Writen instructions on backing up without explorer.exe
I open task manager and then i go to start new task I would go to browse and find what i wanted and right click it and then go to send to and send it to a flash drive or whatever or you could right click the file and maybe you have an option to burn it using real player for music or some other program that can burn files to your cd's.
Vistual instructions on backing up with out explorer.exe
edit: In picture, in the send to drop down menu the foriegn drvie (f:\) is a flash drive.