Hi,
Several of the nasteir viruses, worms and trojans currently doing the rounds of all our email attachments will cause this problem if the hard drive gets sufficiently infected.
Unless you can boot sufficiently long to run a floppy with a virus removal tool like "stinger'' (free download at
www.mcafee.com), you may have to recourse to using another hard drive unit (with antivirus software installed) to boot your computer, with the normal hard-drive installed as SLAVE hard-drive. This will allow you to scan the old hard drive for virus infections and remove them using stinger or standard programmes obviously updated!). Following this, the old hard drive should reboot normally. In severe cases of nasty infection, it might be necessary to completely reformat your odf hard drive with WIN XP SP1/2 - or, if it will do so, just re-run the XP disk on a repair basis. Wither way, whenever you have finished this, and to ensure you have removed all viruses etc, you will need to select PROGRAMME RESTORE function OFF (tab in SYSTEM file of Control Panel)and rescan as many of the newer nasties hide a copy of themselves behind your system restore 'wall'and reinfect the hard-drive on the next boot. Such joy!
The secret is - always install and maintain up to date anti-virus software and run it frequently. Also NEVER open email attachments from senders you don't know!
Hope this helps!