so fed up with this merry go round...
It seems that the repair people and support staff you are getting assistance from (Except here, of course... Speaking of folks like the MS support tech you mention) have no idea what they are talking about. What the MS Tech said makes absolutely no sense whatsoever. What do they expect you are you going to do with the product key to magically start it booting? sing to the PC with it?
Based on what you've said and since the bootable Disc you do have already boots up, the CDs you have are fairly certainly not bootable. (And despite the MS tech's suggestion, you having a product key won't magically make them so!)
It sounds like there isn't but your PC ought to have a "certificate of authenticity" on the case from when you first bought it. If so you can use that product key, and you can get a Windows 7 ISO to install
here (You would burn the ISO to the disc using another PC and a tool such as
FreeISOBurner.
Does your PC have one of those "certificate of authenticity" stickers that are common on PCs nowadays?