Why will System Restore not work?

My PC has gotten a little glitchy over the past few days and after running loadsa scans and coming up with no obvious issues I decided to try restoring the system to a restore point prior to it starting to misbehave.

Every restore point I choose doesn’t seem to want to work, it attempts to restore and when it boots back up again it says it hasn’t been able to restore to said point and that no changes have been made.

Any suggestions as to why this might be happening? I’m using Windows XP Home Edition Version 2002 Service Pack 3