Windows 7: what should I do

I am posting this in the Chill out room, for it is not windows 7 specific.
If a moderator feels it should be in a different category please feel free to move.

The post is tiled "what should I do", but "what you would do" responses are also welcome.

I have a gateway FX laptop, a Gateway FX desktop, and another pc that I built.
there are 3 other laptops that my other family members use no specs below for them, but two are windows 7 home pr 64bit and the other is vista home pr 64bt.

I would like to have a server that I could run a windows program (ultra Hal) from my other 2 computers.
Also I would like to be able to store all my music and other files on a server and access them from any other computer in the house.
I'm also thinking of access to the server by cables (cad5) only, not wireless due to concerns of security.

I do have a few questions for I never had a server before.
1: is it possible to use a server to run a program(ultra Hal), and use it as a storage server at the same time?
2: I do not know if I would need a windows server OS to do this, or can windows 7 handle this task?
3: also what computer should I use for the serve? The one I built, the Gateway Fx desktop, or should I just build a server?
4: if I'm to build a server what are the minimum specs that would be best to do the tasks I want to do?
5: and would I need 2 servers, 1 for the (ultra Hal program, and another for storage?

The pc that I built quick specs:
Asus AT3N7A-1 motherboard
intel atom 330 cpu
Nividia ion for graphics
2gb of ram
40gig ssd << installed in my desktop as primary drive atm
windows 7 home pr 64bit

desktop quick specs:
intel core i7 2600
nvidia Geforce 440
8gb ddr3 ram
intel 40gig ssd << primary 1 partition
1tb hhd << secondary 2 partitions (one for 2nd os and 2nd for shared files)
window7 home pr 64bit + window7 home pr 64bit << dual boot

laptop quick specs:
intel core 2 Dou cpu p8400
Nvidia Geforce 9800M GTs
4 gb of ram
320 hhd << 3 partitions (for 3 different operating systems)
vista home pr 64bit + window7 home pr 64bit + Debian << triple boot