The operating system cost like a hundred dollars if you bought windows 7, if you don't pirate it. You can't even get a pc from bestbuy for a hundred dollars, maybe add another zero.  
 
You could just upgrade the mobo I suppose and get a new card, recycle the ram, psu if it's high enough and case. It will still cost more than a hundred dollars.

This just reads like you're trying to beg free stuff off people.  Whatever good luck with that, I'm sure Starcraft 2 will run on xp though.   
 
Don't you have anything to work with? Case? Mouse? Monitor? Keyboard?   
 
EDIT: Your current PC can't be that bad if it can play TF2.  Why don't you just post your specs and let us see what you have to work with.  I doubt you need a whole new rig.

" This just reads like you're trying to beg free stuff off people.  Whatever good luck with that, I'm sure Starcraft 2 will run on xp though.    Don't you have anything to work with? Case? Mouse? Monitor? Keyboard?    EDIT: Your current PC can't be that bad if it can play TF2.  Why don't you just post your specs and let us see what you have to work with.  I doubt you need a whole new rig. "

If you send me 100 dollars ill send you words of encouragement and belief. That's worth much more then a new rig. 

not gonna happen, unless you bought a stolen PC from some shady guys in the alley.

I just bought a new HDD for my mom's computer and that alone was $37, more than a third of your budget.  I think you could do it for $300 or maybe even $250, but $100?  You aren't going to actually buy much of the stuff in the build. 

ha. building an entire PC out of $100? 
 
good luck with that

Yeah, the PC is going to a friend, I myself have a fairly nice PC right now (core i7 860, 4870 etc.)
Basically I need to come up with a mobo, graphics card, and proc for $100, because I'm pretty sure I can come up with the other stuff from the box of spare parts in the basement.

" ha. building an entire PC out of $100?  good luck with that "

SCII recommended spec is only like 8800, 2.4 ghz dual core.  Honestly its not that bad.
 
@IncredibleBulk92 said:

" This just reads like you're trying to beg free stuff off people.  Whatever good luck with that, I'm sure Starcraft 2 will run on xp though.    Don't you have anything to work with? Case? Mouse? Monitor? Keyboard?    EDIT: Your current PC can't be that bad if it can play TF2.  Why don't you just post your specs and let us see what you have to work with.  I doubt you need a whole new rig. "

cannot be done. simple as that.

That's what makes it a challenge dude.
 Spare parts I plan to use:
- case
- power supply
- RAM
- hard drive (wiped of course)
 
Stuff to buy for $100
- mobo
- proc
- graphics card
 
With the aid of the weekly micro center add I might be able to pull this off.
 
 SC2 Recommended specs

• Windows Vista®/Windows® 7   <- This is going to be XP because I have a license lying around somewhere
  
• Dual Core 2.4Ghz Processor
• 2 GB RAM
• 512 MB NVIDIA® GeForce® 8800 GTX or ATI Radeon® HD 3870 or better

What I meant by freebies was that I wont be BUYING every single component of this build, not that I want free stuff from people. "

Does software count?

" @ReefTrigger said:

What I meant by freebies was that I wont be BUYING every single component of this build, not that I want free stuff from people. "

Sorry mate you'll have to clarify that for me.  I didn't really mean to accuse you of begging for free stuff (although that is exactly what I said) but it seems like you've just said you don't want free stuff but you won't buy everything.  Doesn't make a lot of sense to me.  For my money your either going to have to lift a lot out of your spares parts box or up your friends budget.  I don't think that $100 is enough to buy a dual core let alone everything else you'll need. "

" Does software count? "

You're really going to have a tough time getting what you want for $100. You also need to make sure your spare parts are even going to be compatible with the newer hardware you are purchasing. Most newer motherboards require at least DD2 RAM, and any newer video cards may require a decent power supply as well as the appropriate connectors.

You might have to go dump-shopping. The cheapest dual core processor I could find goes for $50, and mobo around $35. You might be able to find an old, but perfectly fine 8800 that someone is trying to get rid of.

Without downloading illegal software and being a fucking scrounging bastard this is impossible.  There is no way in hell you can do it for $100.  Thats like me saying I can build a car for $100, buying some tires for $60, a new steering wheel for $40 and then getting a free car from my friend. 

Save up your money instead for a decent computer.

Or one can get a job, and purchase somehting better?... ; )

" not gonna happen, unless you bought a stolen PC from some shady guys in the alley. "

get a job.

" Stuff to buy for $100
- mobo
- proc
- graphics card   

Dude, a PS2 (10 year old console) is $100. You're going to have to shell out a bit more to play a modern PC game, even if you have some parts already. You haven't even listed out the parts so how could anyone recommend something without knowing it's compatible or not? You didn't think this through did you?

This is totally possible. Come back in ten years to find out how!

@reeftrigger: i recently buy a core 2 duo tower 1.86 ghz with 1 gb ram 80 gb sata harddrive dvd rom with an 17'' hp lcd with built in speakers monitor keyboard mouse power cables and lcd video cable in just 100 dollars

not worth it, and not possible anyway... even on ebay the ones that 115-149$ range still dont meet the requirements of SCII.....