Question : Ran a disk clean-up and a de-frag

Ran a disk clean-up and a de-frag 2G of memory and computer slow any Suggestions?  
the computer has 4 sticks of 512MB

Answer : Ran a disk clean-up and a de-frag

GO to start>run> msconfig
then go to startup , uncheck all boxes, keeping the antivirus one

also download & run malware byte:

http://www.malwarebytes.org/mbam.php

and combofix:

http://www.bleepingcomputer.com/combofix/how-to-use-combofix