There are alot of free scans on line some good some bad,some cause more trouble than you had before you started,here is a good one,I have used this several times with good luck,its by "windows" thought i would share it
http://onecare.live.com/site/en-us/article/slowpc.htm
good luck
http://onecare.live.com/site/en-us/article/slowpc.htm
good luck