Win2k caching (??) problem

I'm really at a loss to explain this, though I'm assuming it's got something to do with file-caching or something along those lines. I'm running a Dual AthlonMP 1600+ / TigerMP / 1G PC2100 / 10kRPM SCSI HDD (full specs listed below) rig right now, and I'm having performance problems ! As things stand right now, I'm getting occaisional (read: every 20 mins or so) miniscule hangs while my system does something. I'm not entirely sure WHAT it does, but it's enough to occupy my box and make it stop whatever it's doing for half a second.
Aside from that, I'm also having problems that I SUSPECT may be DirectX related (running DirectX 8.1 right now). I'm getting odd caching (I assume) glitches when watching movies / listening to MP3's / doing anything multimedia related. I'll be a few minutes into a movie, and all of a sudden, my Box will drop 15 frames and half a second of dialog, and jump forward (never back though). The audio and video DO remain in sync. I also have the same problem with MP3's, never more than 3/4's of a second worth of skipping, but it's there, and extremely annoying, to say the least
(I should also note that these problems come up, whether I'm running files across my LAN (100Base) or locally.)
If anyone has any ideas / suggestions, I welcome any and all help people can offer as I'm something of a win2k newbie and not entirely sure that I'm not missing something very basic.

--Nic

My Complete System specs are:

Dual AthlonMP 1600+
1G PC2100 Kingston ValueRAM (2x512M sticks)
Adaptec 29160 U2W SCSI
a PAIR of Seagate Cheetah 10kRPM 8G Drives
(Drive 1 used for Apps, 2 for Data, MP3's, Movies etc.)
ELSA Gladiac 920 GeForce 3
Soundblaster LIVE! Platinum
D-Link 538TX NIC
Yamaha 20x10x40 CDRW
Pioneer 16x DVD Drive
Enermax 465W PSU

Software / Drivers:
Win2k Pro SP2
DirectX 8.1
DivX 4.11 codec
All Drivers other than these are recent to within 6 months.