Idon't know why you are having problems loading UFT on your new computer. I assume you are using the program disk. You can try doing an uninstall or just delete the UFT folder if it appears on your hard drive and try installing again.
Do you still have the old computer with UFT on it? If so is it networked with your new computer or... does it have a CD burner? If either of these cases exist you can copy the entire UFT directory to your new computer (either via a network or burned to a CD) and get UFT up and running that way (have to go into Windows Explorer under the UFT folder and click on Uftree.exe to open the program).
You will also need to copy and load the roots font to get your charts to look good.
Others might be able to answer the question of how long TMG will be around. As for me changing to TMG (my two cents). I figure I'm sticking with UFT until it will not run on whatever the latest OS is. At that point I would change to TMG. Of course it appears that you have reached that point already.