Well, I've been playing BF2 on my aging system:
MSI KT3 Motherboard (only 4X AGP)
AMD XP 1600+ (non-overclocked)
512MB RAM (PC2100/266MHz)
ATI Radeon 9600 Pro
SB Audigy 2
Maxtor 40GB HDD (ATA100)
I upgraded it to 1GB RAM a month or so ago and that improved things a bit, but after I found someone willing to sell me a slightly used, but never OC'ed Athlon XP 3000+/400MHz CPU for $60, I decided it was time to upgrade. Now my sound card is pretty good and my video card is decent, but the rest was really holding me back. I ran BF2 in 800x600 with medium settings and it ran at a good FPS with no stuttering, but at the price of that CPU, I figured I could afford a small upgrade. I knew that the RAM I had in my system (@266MHz) would mean that my new CPU would be limited to ~1.75-1.8GHz instead of 2.1-2.2GHz without overclocking, but for $60, who cared? I bought the processor and found out that my old motherboard would support the 3000+ processor with a BIOS update. I did that and then took my PC apart to replace the processor. As I popped the HSF off the motherboard, one of the tabs on the socket adapter - that holds the HSF on - broke clean off. Damn! I knew that it probably had to do with the age, considering that my MoBo was ~4 years old, and I ran the hell out of it. Heat probably made it brittle. I also knew that this simple failure meant that I wouldn't be able to use that MoBo for my new processor. My simple $60 upgrade just got a lot more expensive and time consuming. :x
Not wanting to have to completely reformat/reinstall, I decided that it would be best to try to find the same MoBo on eBay, after all, it was so old, it should be pretty cheap. Nope. Didn't find very many of the model I needed. Oh well. I told my wife what happened and she felt bad and offered to pick up a new MoBo while in town since she was near Fry's. I gave her a model of a mobo that I thought might work well and it turned out that she found a much better model with more features and got a deal to boot. She picked up an Abit NF7-S G2 and only paid $66 for it. Wow. Only "down side" was that it used an nForce2 400 Ultra chipset, which in and of itself wasn't really a down side except for the fact that my KT3 used a Via chipset which meant that a Windows reinstall/repair would be necessary. Once she got the MoBo home, I saw that it had RAID and SATA built in - which was something I wasn't expecting. I decided that I could spring a few more $$ to pick up some new hardware to go with it. I dropped $87 for some Crucial memory (2x512 of PC3200, shipped FedEx 2 day) so I could get the full effect of my new processor, and dropped another $130 shipped for two Maxtor DiamondMax Plus 9 160GB SATA150 drives. Not bad - pretty much a new computer for less than $350. My wife's computer will benefit from the additional memory she'll get as well.
Well, after all this, I am hoping to at least be able to run 1024x768/med for BF2 - though I thuroughly expect that to be attainable given what I could run before the "upgrade". Yes, I plan on a RAID1 array, and not overclocking my Barton - call me cautious, but I prefer stability and redundancy over speed.