Try this
1st method - download the free PAF from Family search and try installing on your computer. If successful, then try importing your genes united file.
http://www.familysearch.org/eng/default.asp?page=home/welcome/simplePAFRegistration.asp
2nd - you may have to upgrade your PC so that your version of FTM will install.
It sounds like your software/computer combination is not right so your FTM is basically useless unless you spec your PC to the minimum requirement that should be written on the FTM packaging.
If your PC is up to spec, create a restore point before the following.
Use add/remove for FTM if there is any sign of it in your program listing.
Manually delete any FTM folder in the programs menu that has been created by previous install attempts.
Try installing again. If unsuccessful then repeat the above but then go to registry method.
Go to start/run/and type regedit. hit ok
Click file export (Backup your registry.)
Select the top computer icon in the left listing then press F3
type in the search bar something like FTM and locate all entries that previous installs may have placed there. Delete them with caution.
(Sometimes a registry entry is responsible for stopping some installs).
Last resort, save everything, wipe your HD and start over :'(
Cheers
Dave