If its Windows xp..... have you installed or changed and software since the date it stopped working???
If no... and it is XP... perform system restore... restore to an earlier time.
Start / All Programs / System Tools / System Restore / Restore to an earlier time / Choose a bold date that was before you were having this issue (please keep date within 10 days of current date if possible).. and continue until pc restarts... This process should not erase and documents, saved works, photos or emails that you have received or created in the affected times. Though this is about 90% true....
I don't gaurentee anything with Windows exept that one day you will see the blue screen of death. ---Hope this helps