Ok if your fans spin up and you don't get video, it can be one of 3 things:
1) CPU
2) Ram
3) Motherboard
More than likely it's either the CPU or Ram, because you won't get video if either one of them is bad. You need to explain "messing around" in more detail. Are you overclocking your cpu? If so, then I would lean more towards your cpu being fried. Basically, you are going to need to go thru a process of elimination. First try to borrow similiar ram from a friend (i.e. take out your ram and use your friends ram). Try booting the system with his memory. If the system still doesn't boot then your memory is ok. Now you have a good idea it is either the CPU or Motherboard. Next step is to either take out your cpu and try to find another motherboard to test it in or get another cpu and put it into your motherboard. Unfortunately, this isn't an easy thing to accomplish, because it's not easy to find older cpus and motherboards to test out your parts. Do you live near a small computer shop? If so, they may be able to take your cpu and put it into another motherboard and tell you if it works. If it does, then you have a bad motherboard. I just had to do the same thing you are doing. I ended up having a fried cpu, but I overclocked my Athlon and I understood that could happen. It lasted me a year and a half so it wasn't a big deal. Good luck.