Cisco VPN with HP Media Center Remote Peer not responding

Brand new HP Digital Entertainment Center with XP Media Center 2005 operating system, trying to connect to work via a Cisco VPN client provided by my employer, is able to dial up my ISP but then gives the message "remote peer is no longer responding". I found a problem note regarding this message that said to turn off my Windows XP firewall (or pop specific holes in it). I turned it off completely first, just to make sure that was my problem....apparently not, same message.

The HP DEC does not come standard with a dialup modem (they figure everyone lives in a big city where they can get cable or dsl), so it's hooked up to a supramax 56k USB modem. It dials out fine and we can surf the web, just can't VPN.

Anyone have any ideas? Followed all the instructions provided with the VPN software to configure my networking options, double checked all settings.

System Info:

From the box:
HP Z540N
Intel Pentium 4 processor 530 with Hyper-threading. (doesn't say speed,
supposed to be 3 gig.)
160 GB 7200 RPM Serial ATA hard drive
512MB PC3200 DDR memory
ATI Radeon X300SE Graphics card with 128 MB DDR memory
Microsft Windows XP Media Center Edition 2005

From The DEC: Windows version:
Version 5.1 (Build 2600.xpsp_sp2_rtm.040803_2158 : Service Pack 2)

From the VPN CD:
Version 8 02-11-04