As I don't have Poser7 anymore, I may just guess but you should see something like this on your library. This is from a Poser11 but you  must have the equivalent button, I suppose that it's easier to find it in floating mode.

You simple have to copy your old runtime to a dedicated folder on your new computer.
For example, in my case, I have reserved a drive for Poser, guess... it's P: :grin:

Once it's copied, retrieve your favorite Poser and add as many runtimes as you want using the "+" button

Oh and if I remember correctly, Poser7 is the last "portable" version: you may move its directory wherever you want on your system...

𝒫𝒽𝓎𝓁

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(っ◔◡◔)っ

👿 Win11 on i9-13900K@5GHz, 64GB, RoG Strix B760F Gamng, Asus Tuf Gaming RTX 4070 OC Edition, 1 TB SSD, 6+4+8TB HD
👿 Mac Mini M2, Sonoma 14.6.1, 16GB, 500GB SSD
👿 Nas 10TB
👿 Poser 13 and soon 14 ❤️