I would scan the PC
for spyware. Use Adaware or Spybot Search and Destroy. Or...see what version do you have by going to Help and then ABOUT. You will see which version you will have. If you have an older version than 6.0 then I would upgrade Internet Explorer to version 6.0....
You may have spyware that will generate these popups and error messages. If your spyware scan did NOT detect anything, then I would do a REPAIR of Windows 2000 which includes repairing Internet Explorer. Or, like I said, if you have an older version of IE, upgrade or download IE 6.0 or 7.0 (for that matter). If your using Win2000, what Service Pack of 2000 are you using? You must have Windows 2000 SP-4.
Good Luck..let us know what the scanner found then I will help you further.
[Edited 2006-02-06 04:17:18]