WinXp Control Panel/Settings Problem

Hey there guys, just joined. Now then, off to my problem. My mom has been having problems with her computer (Dell w/WinXP as OS). These are just a few of them:

-Desktop Right Click> Properties> Nothing Happens (hourglass then nothing)
-Control Panel> Add/Remove Programs> Nothing Happens (same as above)
-System Tools> Disk Defragmenter> Niothing Happens (pretty redundant)
- My mother, who uses Norton (Which I am going to get rid of, as soon as I can and replace it with AVG) tries to open it. An error pops up like this.

"NMain.exe - Bad Image "
The application or DLL C:\WINDOWS\system32\ATL71.DLL is not a valid Windows image. Please check this against your installation diskette.

By the way, im not the GREATEST with computers, but I know a few things. And, if any of you say "Just do a reformat/install" with WinXP, I dont believe I can do that, seeing as im not sure if my mom has the XP CD's. (she got the computer used from her father, who really wasnt on top of that stuff)

I cant figure out what the problem is, and its irritating, to say the least. There are a few other Control Panel options that dont work as well, so its a problem that, while seemingly harmless, is annoying. The error pops up every once in a while and I hit Ok, and the computer seems to run just fine afterwards. So, anyway, yeah, I hope I can get some useful input here and hopefully put an end to this evil error! Thanks all!