I was working on a clients computer last week and he had 512mb of ram on a Windows Vista machine. It’s one of those machines that was released right when Vista was released, and the latest technology then called for 512mb. My job was to increase the performance and speed, the client complained that it was too slow. Theres a problem with machines that are only 512mb of ram and running Vista–You can’t do too much without upgrading RAM. But with what you can do, you can really make a difference with a 3 simple steps:
1. For smaller ram machines, use a USB Stick for ReadyBoost.
You can buy a 4gb Kingston USB flash drive from Amazon here: 
2. Turn Windows Enhanced features OFF
The Aero feature on Windows 7/Vista uses a lot of resources to make your OS look pretty. Disabling it will greatly increase your performance. This is especially useful for gamers or people who don’t really care how nice their desktop looks. To do this on Windows Vista right click your desktop and go to Personalize, then Window Color and Appearance, and on the bottom you should see a link that says “Open classic appearance properties for more color options.” From the drop down list, select Windows Vista Basic to turn off Aero. For Windows 7, the process is like this: Right click on the desktop and go to properties, then Click on the theme “Windows Basic Theme”, or any other theme not listed under Aero. Also, for a little extra speed, on Vista and Windows 7, hold down the Windows key and press Print Screen on your keyboard to open up the System display. Click the button Advanced System settings, Under “Performance”, click the button Settings. From there you can uncheck some things that will speed up your computer. I recommend unchecking things like Shadows under menus and mouse pointer. The idea is to make your computer faster without making it too ugly. I recommend a middle-ground.
3. Turn off Indexing for all your hard drives.
Indexing is what makes searching for files easier in Windows. It remembers all the files you have searched previously and keeps them in a database, but this really slows down your systems performance. Go to My Computer from the start menu. You should see a list of your hard drives. Right click on them (Usually C:, and D:), and click Properties. From there, Uncheck “..allow files to have contents indexed.” When Click Apply, then Ok. At this point Windows will go through all the files on your hard drive(s). It will take a little bit, but when its done, you’ll notice a speed increase on your system. These should help you big time. Leave me a comment if it did!