Since some people are having issues trying to get Windows to recognize their Xoom, I've compiled a list of suggestions found in both these forums as well as across the net.
1) Disable Anti-virus when installing the moto helper (to avoid install problems) & re-enable afterwards - standard practice for installing things
2) Enable USB debugging
3) Disable or allow an exception to any firewalls for the MotoHelper (theory here being that the MotoHelper doesn't actually install the driver, but instead connects to the Moto site to download the most up to date ones)
4) Only use the USB connection on the rear of the laptop/desktop << one that is linked directly to the motherboard and not a secondary USB port. Also, try different USB ports on the back. The front ports may not carry as much power.
5) Use the USB cable that came with the Xoom as others may be older, not rated the same, etc. (it's happened a few times in the forums already)
6) Install Windows Media Player 11. (you do not need to activate or even open it, just install it - something in the package gets some people up and working)
7) Make sure when installing the Moto Helper software, you do NOT have the Xoom connected, then reboot the computer and when it comes back up, then hook up USB cable. <<That is the proper way to install ANY driver - install first, then hook up device.
8) Try installing the umdf drivers from Microsoft here: http://go.microsoft.com/fwlink/?LinkId=71641&/umdf.exe
9) Right click on My Computer, then Select properties > hardware > Device Manager. If the PC is recognizing XOOM as a MTP device, you should be able to see it under "Portable Devices" and copy items to and from Xoom. If it is not there, right click "Portable devices" and select "scan for hardware changes" and see if that causes Xoom to shows up.
10) Some newer ICS kernels may have an option to allow "Fast USB charging" where you can charge off your USB port as quickly as your AC plug. But allowing this option will disable the standard USB connection to your device and show up as "INTF2" attempting to install drivers. If you uncheck this, it goes back to the standard USB MTP connection type.
Hopefully, one of these will help resolve your problem. I'll add more to this as I come across any possibilities.