With the Virus TI unplugged, hold down the "Arp Edit" button, located under the "Master Volume" knob, and plugin the Virus TI. You will see two LEDs (BPM and Logo LED) start flashing back and fourth - this indicates it is ok to now let go of the "Arp Edit" button and let the TI boot. All factory parameters * will return to their original settings.
Alternately, if your TI is off via the "Sleep" fuction (both transpose buttons) - simply hold down the "Arp Edit" button, located under the "Master Volume" knob and the TI will reset.
*note - this does not include factory sounds or banks.