System Restore

[pillainp]

I know this is going to seem like a pretty dumb question, but I think i'd like to know, especially since i am new to windows xp.

I understand the concept behind System Restore, and it's a cool idea, but I'd like some of the gory details as well.
How exactly does Windows XP store and manage Restore Points? What data is recorded? Is it just a backup of the Registry? Where is it stored? Is software installed after the last restore point deleted from the hard disk or is it left onboard and just not recognised due to an earlier registry?

Is it possible to copy restore points to CD or tape and then use them later?
Is it possible to set the number of restore points that are stored and not just the space reserved for system restore?

All help appreciated.

NPP

[HAL9000]

It stores not only registry information, but file information as well. Say you have a new system on the first of the month with a clean install.... you install MS Office on the 2nd, but deleted it on the third., and your favorite game on the fourth. It's now the fifth, and for whatever reason, you need to do a restore. If you do a restore to the third, you will lose the game you installed on the fourth. If you restore to the 2nd, you will lose the game you installed on the fourth, but get back the MS Office you installed on the second. It puts your system back to the state that it was in at that point the restore point was taken.