7-Zip is not a game. Illegal sites are infamous for adding malware to their downloads. Always get 7-Zip from its SourceForge site:
http://sourceforge.net/projects/sevenzip/ You will need to be vigilant after a system restore as a lot of malware will copy itself in the the restore points so that you restore the malware with the system restore. You probably need to do some serious AV scanning of your system. Also, as Draclvr notes, you are more at risk on XP with no more security updates and some security software dropping support for it. Remember, XP is more than a decade old, which in computer terms is ancient.
BTW, 7-Zip will handle all that WinZip does and many more. With just the built-in utility and WinZip you will still commonly encounter type you will not be able to open. It can even unpack some installers. You are better off to dump WinZip than 7Zip, but it really does not hurt to have all. They are small programs and do not conflict with each other after you decide what program you want to open each type.