I modified my computer today. It was a very substantial modification. Honestly, I cannot say that it runs any faster. In fact, it is quite a bit slower if anything. The operating system is not any flavor of Windows or Linux, but an operating system is probably superfluous. There are no functioning USB ports.
It is totally unsuitable for surfing the web; emails are right out. I cannot find an antivirus program that will run on the thing, but I doubt malware will be a problem. Word processing? Forget it. It will no longer read or burn CDs or DVDs. It won't play music or any other sound through the speakers.
Overall, I am quite happy with the mod.
(eta: Actually, that isn't me, and it isn't my computer. But it's really cool, just thought I'd share.)