Using serial and USB both?

[Mr3arnest]

Ive scoured the forum posts and cant seem to find this answer. Help or links to solutions very much appreciated.

I'm just starting my adventures in diagnostics and dont want to blunder through blindly and make mistakes. Thanks for your patience.
I am interested in being able to work on two BMW's of mine. A 1998 e38 and a 2005 e83 X3.
I have a Bcables DCan usb cable and the DVD's with all the programs have been loaded onto a dedicated HP Pavilion running Vista Home Premium with 1982 megs of ran on a 32 bit operating system. (It should be noted at this point that I'm a lifelong Mac guy and Windows is a brand new experience for me. That alone makes it especially challenging and scary.)
For the e83 I had hoped to use the silver D-CAN cable with adaptor into a usb port. When I try to do a setup with INPA I'm led to believe I'm to select the COM1 port but I only see COM3 in the drop down menu. Also there are 3 usb ports on the computer. Does it matter which one I use? I haven't gotten communication between the program and the car yet.
That cable came with a 16-20 pin adaptor cable for plugging into the socket under the hood. I'm not sure that will work for either of my cars and I haven't used it yet. For the e38 i've ordered a 20 pin connector with a Tiny ADS built in and a D89 serial port connector. It should be here tomorrow.

I expect that INPA and its associated programs will be used on the e83 and DIS and SSSProgman will be used on the e38. I have installed

INPA, DIS, SSS Progman, NCS Expert, WinKPF, Navcoder and more that came with the DCAN (Silver Cable) and been told they can provide me with links for
ISTA D & ISTA P which works with F series cars as well as E series cars.

Is this going to work for me for both vehicles when i get the install ironed out or is there something i should change before I get further along?For instance Should I
start over with an XP operating system or install some Virtual PC or program that emulates that environment? For one or the other or both sets of programs?

What other tweaks should i be aware of? If i need to cut bait and start over again I want to do it now.

Thank you in advance for your time, tips and patience for what is likely beating a dead horse for the tenth time for most of you.

Mr3arnest in Vancouver BC
E 38 740i build date 11/97
E83 sometime in 2004 or 2005 (Which reminds me... In the INPA setup window my particular E83 engine wasn't listed. Thats odd, right?))