In the natural course of using your computer you'll leave behind junk data, modify key files and pick up unwanted software.
Vista is significantly better than previous versions of Windows in terms of looking after itself. It regularly defragments the hard drive and runs spyware scans using Windows Defender, but you can still improve on its maintenance schedule.
You may also want to ensure that Windows' key system files are intact and in place. The best way to do this is by using a command line utility called System File Checker or SFC. It needs to run with administrator privileges, so click Start > All Programs > Accessories and right-click Command Prompt. Select Run as Administrator and give your permission to continue. Type sfc /scannow and press [Return]. This runs a scan of the main system files to ensure that they're in place and haven't been corrupted.
Spyware cleaning
Vista's Windows Defender protects against spyware. It's well worth using because you can set daily scheduled scans by Choosing Tools > Options and ticking the box marked "Automatically scan my computer". You can also set the preferred time for a scan and opt to automatically check for updates before scanning. This provides a good basic level of protection but, unlike firewalls, running multiple spyware scans can be a good thing.
One person's spyware could well be another one's legitimate income method. Products from commercial bodies often err on the side of caution. Spybot S&D from
is free and arguably the least compromising of the spyware removal applications. Launch the program, click Update and follow the instructions. Follow this with clicking Check for problems and then remove the high-risk items identified.