The cause of this error can be any number of things.
I would strongly recommend FireFox or Google Chrome browser, because Internet Explorer occupies lot of computer resources which are normally aimed at Servers. Since yours is personal desktop, need a light weight browser like the one I suggested above! Once you get used to this new browser(s), you wouldn't go back to IE any more !
You can have multiple browsers in your computer and choose one as your default one, that wouldn't hurt you.
I would also recommend you having a minimum of 2GB RAM in your System, because Windows consume upto 1GB memory to run its own resources and the remaining would be alotted to its users.
If you believe that the restore point is clean and has SP2 in it then it is not necessary to download any thing from MS. However, if you see the same errors again then please follow the steps that I mentioned in my previous threads. Hope, this will help !