Microsoft has a free* anti-spyware/adware that monitors system changes.
You can set any virus scanner to "scan all files" and if you attempt to download an infected file, it will be obliterated before any problems occur.
(* Its more like a trial, and the program itself was not really made by Microsoft and the definitions are not form Microsoft either)
Any good firewall should have settings to allow you to choose your security level (high, med, low, off etc...)
Norton Internet Security has all of these, you can get a free trial.
McAfee services may also help with these issues, you may also obtain a free trial.
Trend Micro may also help.
Norton:
www.symantec.comMcAfee
www.mcafee.comTrend Micro
www.trendmicro.comDownload the free trials first, as you may want to get the overall look and feel of the program. Test and antivirus scanner at
http://www.eicar.com/anti_virus_test_file.htm and find the EICAR test file.
Note: Never install more than one AV or Firewall at the same time, as it will result in a major problem
REMEMBER: sometime spyware/adware/viruses get onto your computer without your knowledge, scan your computer every two weeks for viruses and always make a restore disk.
(if you want to go free of charge, you can use a free AntiVirus scanner, like Avast or AVG Free, Zone Alarm has a free firewall as well. )
