A game booster is a simple little program that does stuff that you could easily do yourself.
First off, try setting your theme to Win7/Vista Home Basic, or something like that. That'll turn of Aero, which can be a processor hog on a low-spec system.
Secondly, open up task manager and click on the process tab. Anything like "ituneshelper.exe" or some other useless process that you don't need should be ended by right clicking on it and clicking "End Process". Don't be scared of the box that pops up afterwards.
Lastly, and most importantly, make sure your Windows Registry is in good shape by running a registry program like CCleaner. CCleaner is one of the most effective and recommended registry programs on the market, and what could beat it? It's free! By cleaning up your registry, your machine doesn't have to deal with missing entries in the registry and other errors. Most likely, you will have over 100 errors the first time you run it.