You have two issues
FTM 2008 the program
Your .FTM files from FTM 2008
You need to load FTM 2008 from the program CD in the usual way. Personally I would forget about FTM 2008 and buy FTM 2012 as it is about 200 enhancements better and most of the bugs in FTM 2008 have been removed
But if you want to stay with FTM 2008 then install it from the CD, register it, check and install the updates etc
In terms of your .FTM files
The best way to transfer them is from your FTM 2008 in your pre Windows 8 computer, do a File>Backup and save the .FTMB created to a memory stick. This will include any media if present
Create a new folder on your W8 computer and copy the .FTMB files to it. I assume that W8 still has Windows Explorer or some equivalent application?
Now from FTM 2008, do a File>Restore and navigate to where you have saved the transferred file select and open.
FTM 2008 will uncompress the .FTRMB file and open it.
I repeat though, going to FTM 2012 will be a much, much better experience in enhancements, stability and performance