Hi everybody,
I've been lurking these boards for probably a few years now. I REALLY want to get started on my cabinet build (most likely a 4-player cab), but I want to get all the hardware and software up first. Currently I'm on a mac (so can't use this) and I'm looking to get some specs on a pc build. As stated in the subject, I'm completely helpless when it comes to building computers. If any of you guys would be kind enough to help me out with a list of recommendations, I would be so grateful. I've really not wanted to ask this question because it feels like I'm saying, "hey guys, figure this out and tell me what to build", almost cheating... but through all my searching, I haven't really found what I'm looking for. 
Now that that's out of the way.. I plan on using Hyperspin and mostly playing older games, but I'd like the option of running anything smooth; SF4, MK6, etc, so I'm planning on getting a video card. Shooting games would be a plus but definitely not a necessity, I'm looking more for 4 player games than anything else. I'm not saying money isn't an issue, I'd definitely like to keep it as cheap as possible, but I'm willing to spend money. Hopefully I don't get roasted for being so clueless, I just came to a breaking point of frustration trying to make sense of it all

Any input is appreciated. Thanks again.
-David
Deek, as everyone has stated. You don't need a crazy powerful PC to play MAME. Now, as far as newer games go, yes you will need a boost.
This would be my suggestion. Go on craigslist and search "gaming pc" or "gaming computer" and you will find a lot of custom built PCs with good components that people are either trying to get rid of because
a.) they need the cash (for a lot of people, their pricey gaming computer goes for cheap before anything else I have noticed)
or, b.) they are these kind of dudes that always need the latest hardware and upgrade every 3 months (My PC has been going strong for 5 years, albeit I don't play many new games on PC).
I wouldn't be surprised if you scored a PC for 300-500 bucks.
Make sure you don't try and buy a "NEW" rig...these are just guys that buy parts, build the PC and try to sell it for a profit (if you had that much interested in a custom PC...wouldn't one just build it themselves?

)
Honestly, if I were you, I would just ditch the concept of playing those newer games and save the headache. You can built a MAME cab for next to nothing if you are savvy.