Defragmenting the hard drive will usually increase the speed of a hard drive by roughly 10- 15 %. In this case I would say it is more likely that you have spyware, a worm or a virus . If you have no antivirus installed try downloading AVG antivirus from WWW.grisoft.com . ( THey have a free version on this site for home users) Scan the pc and see if it comes up with anything. Also Download Spybot Search & Destroy ( this too is free although donations are accepted, just google it ). This software will scan your pc for spyware. Also Microsoft have a malicious software tool ( also free , just google it ). In general the more recent the operating system the more RAM you should have, for example Vista Home basic uses a minimum of 512 MB RAM, so the more RAM you have a on a computer the better!!
mick
April 2008