I would download and run Malwarebytes first, install it and let it update itself then run on the default settings.
Then download and install Microsoft Security Essentials and let that update then do a system scan.
I would be interested to know how many baddies Malwarebytes finds and fixes !
I wouldn't go by anything regcurepro says. Use malwarebytes and MSE as cyclic suggest. That will take care of any malware/viruses. To clean up temp files ad find any actual registry errors use Ccleaner, one of the programs made by Piriform. Also, test your firewall with the following website: https://www.grc.com/x/ne.dll?bh0bkyd2. I recommend doing at least the File Sharing and Common Ports tests.
The first thing you should do is to increase your RAM to 2 gigs or even more to 4 gigs. That may improve matters a lot.
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