well, windows is a usable operating system, and no doubt the most popular.
In my opinion .... one should just get a fresh installation of windows, put a antivirus program on ---> avast, avg or avira and also have firewall like either comodo or pctools or at worst, keep windows firewall on and you should be ok in terms of protection.
then, get ccleaner and run it (I have setup my pc to automatically run ccleaner's clean function at a specific time I wanted) and also run it's registry cleaner now and then.
also defrag your computer using windows defrag tool or get a defrag tool that you can set up to do the defragmenting on a scheduled basis.
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I have tuneup utilities and it runs fine so far and I have registryfix 7. Both you have to pay for to get program licenses.
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Then it comes down to being careful when reading email or surfing the web