Control Panel: Add/Remove Programs SETUP.EXE won't work

The application will not work when I select a program to remove. I am getting the below Windows error message:
Setup.exe has encountered a problem and needs to close. We are sorry for the inconvenience. If you were in the middle of something, the information you were working on might be lost.

I have installed Windows XP with Service Pack 2. This all started some days back, when I was prompted to upgrade the CA Security Suite in my pc and selected ok. It downloaded the upgrade and I selected it to install. It was installed but the version turned out to be the one for Windows 98 and it buged up my internet access by blocking everything. So, I uninstall that version and was trying to install the proper one but when trying to install it, nothign seemed to happen and after that I got the Setup box flashing briefly on the screen as if it were trying to open a setup/install program. After that I was not able to get the computer to do anything. So, does anyone know what to do now?

Can you try to boot into safe mode and then delete all the contents from the below location:
c:\documents and settings\your user name folder\local settings\temp
c:\windows\prefetch
c:\windows\temp

Thanks for the tips, I will try to do that and report back if its working.

Well, if you are still getting the error message then click on Start and then Run and then type in: control userpasswords2 and then press Enter and then uncheck the box with "Users must enter.." and then click apply and ok.

Thanks for the solution, after I tried the above, everything is back to normal now.