Ok I've been loving the price drops on ram and X2's and I can say that You can build a really nice budget gaming PC for around 500 bucks these days. Here are some parts that will set you you in an excellent Direction to a good cheap gaming system or even just standard desktop.
CPU- AM2 3600, 3800. or 4200.
Start out out your CPU with anyone one of these three awesome processors for the price. They are where Price meets performance right now and if your on a budget look no further. The 4200 went down recently so the gap between these three is now only I think $24 bucks. All 3 will perform pretty much the same but since they are so close you decide. Still I would get the 3600 or the 4200.
Newegg.com - AMD Athlon 64 X2 3600+ 1.9GHz Socket AM2 Processor - Retail
X2 3600- $95
Newegg.com - AMD Athlon 64 X2 3800+(65W) 2.0GHz Socket AM2 Processor - Retail
X2 3800- $102
Newegg.com - AMD Athlon 64 X2 4200+ 2.2GHz Socket AM2 Processor - Retail
X2 4200- $109
Next for ram I highly suggest 1GB of DDR2-677 on a cheap build as DDR2-533 isn't even cheaper. 800 isn't really needed for a cheaper build like this so it's fine.
There are many different RAM choices but my #1 pick is out of stock right now and I suggest waiting for it, or getting one of the other ones underneath that are in stock still.
Newegg.com - G.SKILL 1GB 240-Pin DDR2 SDRAM Desktop Memory - Retail
G.Skill DDR2-677 $60.99
Newegg.com - WINTEC 1GB 240-Pin DDR2 SDRAM Desktop Memory - Retail
Wintec Ampo DDR2-677 $61.99
Newegg.com - SUPER TALENT 1GB 240-Pin DDR2 SDRAM Desktop Memory - Retail
Super Talent DDR2-677 $60.99
Next for a motherboard there are a few different options. I'm going to include the budget boards that will work by just throwing your stuff in but no Overclocking on the first one, minor on the second and nothing really fancy. The last One I will select is a pretty decent overclocker actually but a few bucks more. They will order from cheapest best boards to more expensive.
Newegg.com - ECS NFORCE4M-A (V3.0) ATX AMD Motherboard - Retail
ECS NForce4 (V3.0) $55.99
Newegg.com - BIOSTAR NF4UAM2G ATX AMD Motherboard - Retail
Biostar Nforce4 Ultra $64.99
Newegg.com - BIOSTAR TFORCE 550 ATX AMD Motherboard - Retail
Biostar Tforce 550 $78.99 (This one overclocks really well for its price)
Alright moving on, we'll touch on the Hard drives now. I'm gonna give ya a few different. The will only have 8mb cache and really small capacity but is still very good on a cheap budget. The Second two will have 16mb cache but more space respectively.
Newegg.com - Western Digital Caviar SE 80GB 3.5" SATA 3.0Gb/s Hard Drive - OEM
WD 80GB SATA 3.0 8MB Cache $42.99
Newegg.com - Western Digital Caviar RE 160GB 3.5" SATA 3.0Gb/s Hard Drive - OEM
WD 160GB SATA 3.0 16MB Cache $62.99
Newegg.com - Seagate Barracuda 7200.10 250GB 3.5" SATA 3.0Gb/s Hard Drive - OEM
Seagate Barracuda 7200.10 250GB SATA 3.0 16MB Cache $74.99
Now for the Case. I'm going to give you three of my favorite ones as you can choose many many different. The first is the cheapest of cheap with a PSU that will keep your system cool enough. The second will be a nice Scorpio with 420w PSU with really good cooling for the price. The Last one will be one that has the best cooling and NO PSU if you choose to buy a PSU seperate.
Newegg.com - Rosewill R103A Black Computer Case - Retail
Rosewill W/350W PSU $25.99
Newegg.com - RAIDMAX Scorpio ATX-868WBP Black Computer Case With Side Panel Window - Retail
Raidmax Scorpio W/420PSU $45.99
Newegg.com - COOLER MASTER Centurion 5 CAC-T05-UB Black /Blue Computer Case - Retail
Cooler Master Centurion $44.99 NO PSU
Now for the Video cards. It is really hard for me to suggest anything other than a 7600GT for any kind of moderate gaming as nothing even comes close in its price range really. I'm only going to show you two, one for very light video editing that is superior to onboard and you want to be cheap, or the 7600GT which is very powerful for the price and will max out a lot of games today at 1024x864 res.
Newegg.com - EVGA GeForce 7300GT 256-P2-N445-LX Video Card - Retail
EVGA 7300GT $69.99 This is a a far superior upgrade to onboard and can still offer ok frames at low res in games.
Newegg.com - EVGA GeForce 7600GT 256-P2-N615-TX Video Card - Retail
EVGA 7600GT $109.99. This is awesome for the price and will let you game pretty darn nice at lower res.
Now I think it's a good time to suggest PSU's. I will suggest 3 different ones. The first Being one who's brand is known to work well but not as trusted as the other two. It's cheaper though and it probably work, especially for a lower-end system like this. The other two are trusted brands with each one having more watts depending on your card choice.
Newegg.com - Rosewill RD400-2-DB 400W Power Supply - Retail
Rosewill Stallion 400w $29.99
Newegg.com - SILVERSTONE SST-ST365 360W Power Supply - Retail
Silverstone 360w $38.99
Newegg.com - FSP Group (Fortron Source) AX400-PN, RoHS, 12cm FAN, version 2.2, 2 SATA, 20+ 4 pin, PCI Express, 400W Power Supply - Retail
FSP 400w $43.99
All three will run a 7600GT really though and even though, even the 360w Silverstone.
That looks like it's it on the basic stuff. This really was just something for me to do as I'm bored and was excited ram and X2's went down and I wanted to see what good parts there were for an X2 system. I'm sure it will get barley looked at but hey I had fun haha.