After a few years you may have added up a lot of software you no longer need. Even if you don't use it things clog up your memory through startup listings.
Do all of the following to make your computer faster:
- Uninstall everything you no longer need
- Press Win+R and enter
msconfig
. In the Startup tab you'll see alot of listings for startup items. Some you may not need (exercise caution and dont just disable everything)
- Install a faster and lighter antivirus. MS Security Essentials and Avast have worked well for me.
- If you don't have an antivirus there's a high chance your issue is a virus, so install one
- Upgrade your components if you can. My Vista laptop came with only 1GB of RAM. 1GB!!
- Consider upgrading to Windows 7. They've done a pretty nice job of making the OS more efficient, you'll notice it eats less battery on laptops as well.
- Get rid of any toolbars for Windows Explorer, Internet Explorer or Firefox.
- Get rid of any Explorer context menu items
- Update your drivers and software, as it may be buggy apps hogging resources
Seriously though, uninstalling things you don't need, and having a light antivirus will help you out.
You can get a good view of what's making things slow by using something like Process Monitor. Having said all that, there could be annoying programs that remain which is where a format could do some good.