I need advice about a software / hardware problem: I keep being redirected in Firefox...

Here’s the thing….......
I keep being redirected to oher websites with firefox.
I’m using a Dell Latitude D620 Windows XP Pro SP3 and firefox 3.5.6
I’ve tried running RegCure, Adaware, Spybot, hijack this and anti malware and it keeps happening. I’ve uninstalled all add-ons in firefox too.

I’ll do a search on google, then click a link and it takes me to somewhere totally random, (not porn sites or anywhere specific, although once or twice it has taken me to porn but it seems totally random. if I click the back key it takes me to where I wanted to go. Not exactly life threatening but highly infuriating!

Does anyone know what is going on?
What else can I use to fault find and fix it. it’s driving me up the freakin wall!
I got a wee bit help from a nice chap on a forum but it’s still happening. I cant do a restore, and re-installing firefox does’nt help. I prefer Firefox to I.E. or Opera (the re-direct does’nt happen on them by the way)
Am trying to avoid a full re-format (my PC has just been rebuilt)

Any ideas out there?