Where are you based Ian? I'm happy to take a peek at your lap top.
What I would suggest is buying something like this:
I use many of these in the recording studio and for the remote storage of any data that I don't want to lose. Very cheap and hugely reliable.
What you probably need to do is have a go through your system with someone who knows what they're doing to give it a tidy up - removing programs you don't use (control panel, add/delete programs) and perhaps downloading cc cleaner to tidy the registry.
Cookies are tiny - but it could be your cache needs emptying, this is the place where every web page you've looked at is stored... it can be quite memory intensive.
If you get stuck, PM me and I'm happy to help....