I'm sorry none of us responded to your post, Bruce!
See if the steps for ArchiCAD 9 on Windows 7 here:
http://helpcenter.graphisoft.com/technotes/operating-systems/windows-7/
help you proceed. If not, it is probably an issue with the installer not being compatible with Windows 7. If you can copy your entire ArchiCAD 8.1 folder from Program Files on your old XP machine onto your Win 7 machine...it might run if you have Windows 7 Pro or Ultimate and run in "XP Mode". Right click the archicad.exe file and choose Properties... then the Compatibility tab and check the box for "Run this program in compatibility mode for" ... and select "Windows XP (Service Pack 3)".
No guarantees.
😉
If you do manage to get the installer to work (vs copying your old XP program folder) ... then you'll need to run the latest update patch to bring 8.1 to it's final version with the most bug fixes:
http://www.graphisoft.com/support/archicad/downloads/USA81.html
The latest (last) library for AC 8.1 is also linked there.
Karl
AC 28 USA and earlier • macOS Sequoia 15.4, MacBook Pro M2 Max 12CPU/30GPU cores, 32GB