I've had very good luck with a number of free utilities. I like CCleaner. It's a cache cleaner. It will get rid of any and all temporary files that are serving no purpose. I will use the disk and registry components of that to remove unused reg keys. The best anti spyware utility I've found is called Malwarebytes Anti-Malware.  The free version of that does a very good job of cleaning. I do the updates and scan about once a week. I also use Super Anti Spyware because it has a memory resident component that offers real time protection. All three can be obtained from majorgeeks.com I also periodically use the Wise Registry and Disk cleaners. The coolest thing about the wise reg cleaner is that it has ability to defrag your registry. Obviously you also want and need virus protection. I like McAfee a lot better than Symantec. Symantec seems to have too many issues. AVG is pretty good - for free. Microsoft just came out with a free anti virus program, but I haven't played with it yet. There are others of course. The main thing is to 1) make sure you're checking for updates at least once a day; and 2) make sure to scan your system at least once a week. Something may have gotten on before a def came out. Running the scan will find it before it goes live. Within Internet Explorer, make sure to delete your temporary files when the browser is closed. Tools, Internet Options, Advanced.  Get rid of older versions of programs. Java (which I can't stand) is the worst of them all. Each new version is not an upgrade, but a brand new program. The idea behind Java is great, but they, and many java developers, fail miserably in maintaining backwards compatibility. So, your app that was written for one version may not work on the latest. Go into control panel and remove the ones you don't want or need.  Once infected, many viruses/spyware will prevent you from installing utilities to remove them. For that, boot into safe mode - hit F8 when you see the "starting windows" CCleaner has a slim version that doesn't install the program. It just runs. Make sure to keep up with the latest patches. Upgrade to 7 or Vista if you're still on XP. The kernel is much more protected. If still on XP, I'd try the Root Kit Revealer. The gotcha is that you have to know what the system is supposed to look like when it's clean to be able to compare.  If still unsure, MS (the company, not the guy) has some cool utilities that they purchased from Sysinternals. The one that works best to see exactly what your machine is doing is called Process Explorer. remove anything from teh startup folder that's not necessary. Remove stuff from auto running. Start, Run Regedt32. Navigate to hklm, software, microsoft, windows, current version, run.....google any executables you don't recognize to see what they are. Nuke 'em if they're not important. ah...I could go on and on. It's tough to condense years of practical advice into little snippets that people can use.  hope that helps Jon