Originally posted by: Howard
Desktop just means something atop a desk... However, even if you stuck to the common usage:
Cooler Master ATC110 with a really sweet paint job to match some guys car.
PC Power & Cooling Turbo-Cool 475-PFC
P4 2.53 oc'd to 2.85
Alpha Novatech PAL 8942 heatsink
Asus P4T533
Samsung RIMM4200
RAdeon 9700
Audigy gamer
Two WD1200JB's raid
Liteon 48x
Pioneer DVR-A04
Sony F520 Monitor
Sharp LL-T1820 LCD
Klipsch 5.1
Intel NIC
MS keyboard and mouse
XP Pro
I'll leave the case, as no case is perfect for everybody.
PC P&C has a power supply more powerful than the one they listed. The Turbo Cool 600 Sun Ultra AXmp, to be specific.
A dream PC wouldn't necessarily need to be OCed. I leave this one alone.
A heatsink and a fan... Definitely not the best kind of cooler, and definitely not the quietest. If you want to get outrageous I'd have vacuum-insulated line going to a deep freezer @ -60 C filled with 3M Fluorinert FC-87. Don't get me started, there are even better solutions out there.

I'll leave the motherboard alone, as some may not need gigabit ethernet, fiber channel host bus adapters (great for some sweet storage), SCSI RAID, etc. But since this is a dream PC...
Samsung RIMM4200? That's like walking into McDonald's and asking, "Could I have a combo"? Unless you forgot to type something, of course.
Radeon 9700 I leave alone.
Audigy Gamer? Just for the software, eh? The TerraTec 6fire DMX has better sound quality, although it doesn't support EAX 3.0
IDE drives in a RAID? Could have used a SCSI controller (RAID preferred) and set up some SCSI sweetness. Solid state storage would have even been better.
The media and monitors I'll leave alone.
Multimedia speakers for a dream PC? Come on, just pick something from a decent audio store!
MS mouse and keyboard... Again the McDonald's thing. Less so for the NIC. Unless it's another omission.