Hibbie,
hopefully Steve's right, but before you uninstall you might consider a couple of things mentioned in this thread on a similar topic.
http://www.sonycreativesoftware.com/forums/ShowMessage.asp?ForumID=12&MessageID=802058
Remember that up to v.11 VMS was only 32-bit, v.12 is available as 32-bit AND 64-bit. The 32-bit plug-ins will not work in 64-bit versions.

Why uninstall the old version? .... there may be something in the new version that does not work .. or does not work correctly.

Keeping the old version gives you the option of working on a project if the new version won't. You can keep both (or even three or four) versions on your computer at the same time without any problem from Sony.

I upgraded to Version 12, and started converting all of my Version 11 files. I was also about to delete Version 11. Fortunately, I opened some of the Version 11 files I had coverted and found so many speical effects were not working properly - I sighed a sigh of relief that I hadn't deleted Version 11 and had back-ups of the Version 11 files I had converted.

I put in a technical help request to SONY four weeks ago to address the problems I'm having with Version 12, and other than an automated email saying they'd received my request for help, there's been no response since.

Point being, brighterside is wise to say, "Keeping the old version gives you the option of working on a project if the new version won't."

Also note that once you open AND SAVE in a newer version YOU CAN NOT OPEN that file in the older version ever again.

So it's a real good idea to open that older version (in the newer Vegas) and SAVE IT WITH A NEW NAME so that if you need to go back and work on the project with the older version you can.