slow computer

I had a problem with a laptop that i had to slipstream a driver in the os copy. Thants to great advice i got I finaly got that coputer working and now it is fine. Now I have another problem with the other laptop. I love learning about the slipsteaming and reinstall, so i got this bright idea to reinstall the os for a dell laptop because the computer was slow realy slow.The spec are windows xp sp2 fsb 566 and 256meg ram at 1.2ghz and wireless. After the reinstall it was even slower. The computer is about 6 yrs old. any sugestions on how to increase speed or back to its speed before.