easiest way is to use system restore to back to when it was there
Click Start, point to All Programs, point to Accessories, point to System Tools, and then click System Restore. System Restore starts
On the Welcome to System Restore page, click Restore my computer to an earlier time (if it is not already selected), and then click Next.
On the Select a Restore Point page, click the most recent system checkpoint (in bold) before you had this error or a few days before that and then click Next. A System Restore message may appear that lists configuration changes that System Restore will make, Click OK
On the Confirm Restore Point Selection page, click Next. System Restore restores the previous Windows XP configuration, and then restarts the computer.
the pc will restart and hopefully say "your system has been successfully restored" if not a message will say
"no changes have been made to your pc"