WINDOWS XP NOT CREATING SYSTEM RESTORE POINTS
I had this problem and not one of the usual tips would solve it.
Then I discovered why.....
I had an EXTERNAL hard drive plugged in to my PC for making back ups to....and it was full
So before you start digging very deep just unplug ANY external drives and memory sticks and then try again.
If that does not work then start here (random site I have no connection with, but looks like good advice.).
Helpful???...... then pay up