you installed IE7 for what reason? IE7 is buggy and still broken, and does not play well with XP. You might try a System Restore.
OS, Win XP Home, SP 2, fully updated.
I open IE7 and open multiple tabs. If I go to close only 1 tab, the entire browser closes and I get the "Internet Explorer has encountered a problem and needs to close" message, followed by the same message for the Dr. Watson Postmortem Debugger.
I've scanned for viruses and other malware with none found.