Processor compatability and fan

Trying to fix my brothers old computer that was a custom build and has a microstar-6540 ver.2 S478 motherboard socket. I did a little research, I guess I can take a P4 processor with a 800mhz max speed. I guess I can choose from Celeron/northwood or prescott? Well, I want to choose the right processor for the computer, it's all it needs. Plus I think i need a new fan. But if it's a fan i can take out of one of my random, some older, PCs, then I'll just switch a fan out from another one. But if the processor needs a specific fan to run right and not over heat, i'd like to know. Apparently the case it's in seems to gather alot of heat inside of it for some reason. A friend of my brothers tried to fix and opened up the computer and basically ripped the processor out of the socket and pretty much damaged the pins on the original processor it had in it. unfotunately i'm not aware of what specific processor it was. The sockets still look alright so i guess I'll be ok. Anywho, you're advice please!! Thanks people! Overall, I'm curious of what kind of processor will fit this motherboard, some one please help me out. THanks! Chris

Well, when I plug 6540 into the MSI website, I get this list. So you have a wide choice to choose from.

BUT! Understand when upgrading an older computer, the best bang for the money is not with the CPU, but rather RAM, then better graphics. If it has less than 1Gb, get RAM first.

If using the on-board graphics solution, then replacing it with even a budget PCI card will improve over all performance significantly. Not only is the card's GPU (graphics processor unit) likely to be more powerful than the on-board GPU, but the card will be populated with it's own RAM, optimized for graphics processing. This is important because then you can disable the on-board (if not automatic). This frees up the system RAM, typically 32 - 128Mb, that was previously snagged by the system and dedicated to graphics, in effect giving you a little extra RAM boost in the process.

CPUs vary by type and horsepower and consequently, vary in cooling requirements. Just because a fan physically fits, that does not mean it moves the required amount of air (CFM - cubic feet/minute) for proper cooling for that CPU. So you cannot just grab one that is laying around. And of course, you need to make sure the TIM is properly applied (see sticky, Thermal Interface Material).

WARNING: Older systems typically came with power supplies barely adequate to support the equipment installed at the time. Use the eXtreme PSU Calculator Lite to determine your power supply unit (PSU) requirements. Plug in all the hardware you think you might have in 2 or 3 years (extra drives, bigger or 2nd video card, more RAM, etc.). Be sure to read and heed the notes at the bottom. I recommend you set Capacitor Aging to 30%, and if you participate in distributive computing projects (e.g. BOINC or Folding@Home), I recommend setting TDP to 100%. Research your video card and pay particular attention to the power supply requirements for your card listed on your video card maker's website. Then look for power supply brands listed under the "Good" column of PC Mechanic's PSU Reference List. Ensure the supplied amperage on the +12V rails of your chosen PSU meets the requirements of your video card. Don't try to save a few dollars by getting a cheap supply. Digital electronics, including CPUs, RAM, and today's advanced graphics cards, need clean, stable power. A good, well chosen supply will provide years of service and upgrade wiggle room. I strongly recommend you pick a supply with an efficiency rating equal to, or greater than 80%. Look for the 80 Plus - EnergyStar Compliant label. And don't forget to budget for a good UPS with AVR (automatic voltage regulation).