I got most of this from wmpoweruser.com, see the original article here. Thanks a lot to Kuo who figured this out!
The only addition for me was figuring out the initialization command as the one that was originally mentioned didn't work for me on TMobile USA.
Download HTC Sync for Android from HTC for USB Modem driver for 32bit Windows from HTC’s site (the whole package) or for 64bit systems just the driver here.
I just used the driver (second link) on my Windows 7 x64 and bbowman confirmed the full package from HTC's site working for x86.
Unpack the driver and edit both HtcUsbMdmV64.inf and HtcVComV64.inf. Replace the HTC device IDs with VID_05c6&PID_3199. Leave the &MI_00.
Start the EM diagnostic app on your Dell Venue Pro (##634#), and go to Service Center. Switch to composite mode – password is *#301#
After rebooting the phone, open device manager. Select the first unknown device (USB\VID_05C6&PID_3199&REV_0000&MI_00). Select update driver and point to the root of the two folders (it looks like it’s using HtcUsbMdmV64).
Connect device to PC, open "HTC USB Modem" in Device Manager and select "Advance" section and under "Extra Initialization Command" add the following:
Create a new dial-up connection with HTC USB Modem, dial-up phone number is *99# .Just connect without user name and password.
Hope that helps, the above procedure worked fine for me :)