Drivers are one thing that are hard to find for XP 64, and the dongle needs them to run. If you have a legitmate registered license, I might contact MecSoft directly for a solution. You might also check with them to see how VM runs in 64.
Another thing you can try is going to the Sentinel website and downloading the latest dongle drivers. Their drivers support XP 64 according to the info on the site.
Look here:
http://www.safenet-inc.com/support/tech/sentinel.asp
If that doesn't help, you're probably going to need some e-mail or phone support from either MecSoft or Sentinel or both. --ch