Yes, it will work just fine. Any
USB GPS receiver ever included with any version of
Microsoft Streets and Trips will work with iNav
iGuidance, and also with most other programs. Even non-Microsoft GPS receivers, which work with S&T, will work with iG. There is no need to buy a new receiver if you have a receiver you are happy with.
The one included w/S&T 2007 was GPS-500 made by Pharos. It is based on the great SiRFstarIII chipset. It is the same unit which is still being included with S&T 08. It was for the first time included in some of the last shipments of Microsoft Streets and Trips 2006 in the second half of 2006.
I bet there are many iG users using just the same GPS receiver that you have from the S&T 07 bundle

.