If you're using XP Start>All Programs> Accessories>System Restore and click on "restore my computer to an earlier time" you'll find a calendar showing them for the current month, they'll be a blacker print.
Press Enter and follow the on-screen prompts to restore to an earlier date/time
if will not boot to commamd prompt then:
Restore from recovery console
boot from the XP CD. Start Windows Setup and press R to access the recovery console. Select your Windows installation, then type the administrator password – press Enter if there isn't one. Now enter the following commands:
CD C:\ CD "system volume information\_resto~1" DIR
You'll see a list of restore point folders with names such as RP1, RP2 and so on. Pick the restore point you wish to use, using the folder date stamps to guide you. Enter the commands:
CD RPx (the restore point you chose) CD SNAPSHOT
This takes you into the folder containing the restore point snapshot files. Copy the Registry backups so that they overwrite the existing Registry files.