A/V sync issue

[AC]

I'm trying to build a DVD with MPEG2 files as my source. However no matter
what program I use (I've tried Roxio Easy Media Creator 7 & ULead Video
Studio 8), I am experiencing a progressive audio syc issue. At the beginning
of the production it's not noticeable, but by the end of a 45m production,
it's about 1-2 seconds.

I experience the same effect when I use DV-AVI files as my source for my
production, but the OOS issue isn't nearly as bad as when I got from
MPEG->AVI. I also get the same effect when I convert MPEG2 -> AVI.

I don't think it's an issue with my hardware (see below), but more of an
issue with a setting/driver/codec. I've tried numerous things and out of
ideas. While I'm an experienced .NET developer, I'm somewhat green to A/V.
Before running the production, I shut down all background processes that may
affect it (such as MSN Desktop Index, antivirus... you name it). I'm not
sure what to look at next...

Hardware:
P4 2.4Ghz w/ HyperThreading
1GB DDR
30GB OS/Programs drive; 300GB data drive (seperate physical drives, 1
partition on each)
ATI Radeon 9800 Pro 128MB
Audio is onboard my Asus MB
WinXP Pro SP2 (with all avail hotfixes installed as well as DirectX 9.0)

Ideas?
-AC