will reinstalling windows speed up my PC?

[donaldplozha]

Reinstalling Windows means installing a CLEAN copy of the OS and thus removing all software, drivers and other programs you might have installed until that time + removing any possible virus/spyware/rootkit that might be in and that you don't know about, which of course will speed up your freshly installed OS. Afterwards, though, it all depends on the software you install and on how careful you are with USB-s, CD/DVD-s and browsing the internet which is highly probable to infect your OS with malware.

[scilef]

Have you tried using utility programs like TuneUp Utility? Usually any computer would slow down after repeated use for a good amount of time. Registries get dirty especially after uninstalling programs, there will be broken shortcuts, system startup & shutdown needs to be optimized, & etc. Sometimes, the hard disk needs to be check for errors. There are plenty of utility programs to choose from and you can select which works best on your computer.