Hey, found a solution to this error, simply just keep trying till it works. I left the installation of NEt 4.0 for a while and it just installed itself sucessfully.
As for the ssolutions you found Kesume, the page was great, but the software I downloaded just told me of the problems I already knew, and to fix
them I;d have to fork out £70....in my opinion I've already paid for the OS therefore support for any dodgy update should be free irregardless of whether it's from microsoft or someone else.
Anyhoo, it's safe to say this topic can be closed. Thanks for all the help guys!