OK. I just recently had this happen. WHAT IS HAPPENING The error comes up saying "C:\WINNT\system32\rundll32.exe is not a valid Win32 application" whenever I try to access Control Panel programs, Internet Explorer, Notepad, and pretty much any program. Also, my desktop wallpaper is now gone and just a darkish gray background is there instead. I can't install any antivirus programs, NOTHING!!!! I occasionally also got a random pop-up, whereas I didn't before I downloaded some Zango thing (or whatever it's called). I uninstalled it and ran an old version of Panda Internet Security, but it seems that didn't fix anything. It seems to boot normally and show my desktop wallpaper and load the taskbar icons. Then the wallpaper goes gray and shows all my icons and everything, but I can't run any programs at all!!!!! POSSIBLE CAUSE The only thing I can think of that may have caused this problem is that Internet Explorer had frozen up, so I hit Ctrl+Alt+Delete and went into Task Manager, and I thought I clicked it and so I hit "End Process". It froze, so I clicked again, hit "End Process" again. Did it again and again, with no results. Finaly it showed I had selected 4 different rundll32.exe processes and ended them. That's when my computer started going haywire. I have no idea what's going on. Please help me!!!! T_T OK. Since it seems people take their time responding to this stuff, here's what I tried: I know my parent's computer uses Windows XP as well, so I copied their working version onto a flash drive and replaced my old rundll32.exe after backing mine up on the desktop and flash drive (in a separate folder). Still the same problem. Even though the error says it's rundll32.exe specifically, is it possible theres something wrong with other files as well? PLEASE HELP ME!!!! I've backed up all my files I want to keep on an external hard drive. Would it just be easier to wipe the pc clean, install XP again and then reinstall the drivers and drop the files I want back in, then let the computer auto update? Or should I format just the C drive? 6/6/08 Well, time is important with this issue, and it's been over 18 hours since I made this post. If I'm unable to receive help from anyone by the time I get back from work tonight, I'll just do it myself and hope for the best. At worst case I'll need a new desktop, but I'll enjoy blasting holes in it with my 12-gauge and SKS.