Dell Inspiron 9100 factory restore

Anyone knows how I can restore my DELL laptop to its original factory settings?
The windows XP restore only bring it back about 2 months.
It did not come with any CD that say "System Restore".

I have had this laptop for about 4 years and it's starting to be slow.
Thank you

It did not come with any CD that say "System Restore".
Just about all newer latops don't come with CDs either

They have a hidden partition accessed by pressing a certain function key (like F6 or F10 or some other key on system startup)
If you have one of these hidden partitions (and therefore a startup screen prompt) select the key that starts the System recovery.

Or chat with Dell, if yours has that option: http://www.techspot.com/vb/showthread.php?t=100658&highlight=Chat