whether or not if an upgrade is viable depends on many other factors than just your CPU.
for example, you can't just take out your old processor and toss a new i5 2500k CPU in it. It won't be compatible, and it simply won't fit.
with that being said, you can find out a lot about your computer by running this program here
. don't worry, it is virus free. I promise
you may also want to open the side panel of your computer and check out the wattage of your power supply unit. there should be a sticker that looks like this
. if you overload the power supply with new upgrades, it could start on fire or explode.
if you do decide to build a new computer, you may want to stretch your budget a bit. considering a new copy of windows alone is about $100 dollars.