well, as ghosthunter said, u need a powerful CPU, lots of RAM and a bigger Hard Drive for video editing...

before buying a PC set, consider first your budget. Since you said that your budget is 15 thou, most probably your rig should be AMD based PC. Intel CPUs are pretty expensive for a 15 thou budget.

Motherboard:
well for me, the first important component to choose is the Motherboard and the chipset that goes with it. A powerful CPU will not be as powerful if the motherboard is not good. Worse, a bad one is not stable. For now, the best budget chipset that I can think of is Nforce 2 Ultra, KT400 or the KT600 chipsets. Any brand (ECS, ASUS, MSI, Epox etc...) of a budget motherboard is good as long as the chipsets i mentioned is featured in the motherboard.

CPU:
AMD XP CPUs are your best bet for budget PCs.

Memory:
at least 512 megabytes. pero video editing needs at least 1 gigabyte RAM. but 512 megabyte will do just fine. Any brand of memory will do.

Hard Drive:

Seagate or Maxtor. If your budget still permits, try buying with 7200 rpm hard drives.

CD ReWriter:

Lite-On, or Sony, Samsung, LG brands are good. Don't buy ASUS CD ReWriters. I've heard people with horrible experiences with ASUS CD ReWriters.

Video Card:
Geforce 4 MX cards are the usuall budget Video Cards out there. If budget permits, Geforce FX is the best choice. Or, you can buy Radeon based Vid Card. For the Geforce based cards, there are brands like Inno3d & Sparkle for the budget minded. For the Radeon based cards, there brands like Powercolor or Gecube brands for the budget minded.

Sound Card:
Since your budget is very limited, you could stick to the on-board soundcard found in your motherboard. You could hook 4 or 5 satellite speakers and a sub-woofer in your built-in soundcard. What I did is I put the satellite speakers to the corners of my room preferably in the ceiling, making my bedroom into a surround movie theater.

Where to buy/assemble:
PC Express, Rising Sun, PC evotech.

hope this helps.........