I am having a problem trying to get Quake3 running on one of my
machines.
It starts up..but it's "jerky" abd the sound seems to "repeat or echo"
all the movement is all jerky too.

heres the specs:

WinXP Pro SP1 .... Fresh install plus all M$ "must have patches"
Mid Tower ATX Case 400 Watt
ABIT KD7-Raid
XP 2800+ Thornton 333FSB OEM & VANTEC AeroFlow VA4-C7040
Samsung DDR333 512MB (2.5 3 3 7 T2)
AGP Leadtek GF2 Ultra 128MB 3ns DDR, BLORB Cooling Kit.
Philips Dynamic Edge Sound card
Onboard NIC
Onboard HighPoint 372 ATA133 RAID
2X Maxtor 40GB EIDE ATA133
HP300i DVD/RW 8/24/48
HP CDWRITER-Plus CD/RW
Generic 104 Win98 KB
MS Explorer Optical Mouse v3.0

I have the latest drivers for the soundcard, HighPoint, NIC and
VIA Chipset, the Video card is using 41.09 XP drivers (nVidia ref.)
wich are just fine for an older card like this.... I've only ever used
40.41 and this one, 41.09 on this card.

I had all this kit in another case that was running W2K Pro SP4
with a XP2600+ 226 FSB and a no-name brand crappy sound card
................and Quake3 ran fine.
the rest of the system seems to work fine - Quake2 runs fine as well.
This has me baffled.... any help please

UPDATE:
I guess jerky is the wrong word. Movement and sound sort of has a
Rhythm, it comes in "pulses" if you fire the shotgun you hear:
bang...bang...bang .... at least 5 times and the visual of the shot
is "jerky" in time with the sound....???
Performance improves (slightly) when crappy visual qulity is selected.
Oh yes, it's running Directx 8.1