I built a budget system that ran Source games at 1024x768 all on high w/ no aa/af at 25-60ish fps. very playable for him.
It cost bout $300, cept we had a leftover 20gig HD and dvd drive and a copy of XP.
You could build the same system and just add in a 6600GT or 6800GS if he complains.
Look at newegg or Mwave for the parts (I did the Mwave cpu bundle with the cpu, mobo, and memory and and saved a few bucks and got farcry free.)
Sempron64 2800 (the higher the number you can fit into the budget the better)
Biostar G6100M-7 s754 mATXmobo (or the ASRock version looks to be ok too)
Ram- get him a minimum of a gig try to get Corsair or OCZ value ram
Case I used an Aspire X-Qpack, it's an awsome small cube. It was a tight fit, but it worked out fine.
NEC DVD Burner-$40 or just drive $20 from newegg
HD- Nab a SATA I or II drive.. 40gigs runs bout $40ish and 80 is about $50ish I'd recommend Seagate
Grab a cheap floppy drive with a matching front panel.
Toss it together with BF2 (and HL2 because you must own a copy of HL2 if you own a functioning computer) Just start up BF2 and see how it runs on the integrated GFX.
If he whines about not fast enuf or doesn't look good then,
Grab a 6600GT (~$120-~170) or better yet a 6800GS (~$200)
and tell him to shut up.
Also, I love Macs, but they're no where near practical for anything but to be nice anymore. OSX became diffucult to navigate too... Still like 'em, but much rather have my system than a mac.
In The Mail!!!!- Athlon 64 3500 @Stock/Abit K9N SLi sAM2/2GB G.Skill DDR2 800 @Stock /XFX G7900GT XXX 520/1500Mhz/74GB Raptor w/ 16mbcache/300GB 16mbcache SATA HD/NEC DVD-RAM Burner/OCZ ModStream 520watt psu/ThermalTake Armor Jr./Logitech EX110 mouse/keyboard