Problem:
How do I install IRIS 8.7 from a current installation of 8.5?
Solution:
Copy C:\TT directory somewhere safe.
Uninstall IRIS
Reinstall from IRIS CD 8.5.5
Upgrade from IRIS CD 8.6.3
Upgrade from IRIS CD 8.7
Upgrade from IRIS ServicePatch 87SP3
Upgrade from IRIS ServicePatch 87SP4
Upgrade from IRIS ServicePatch 87SP5
Rename C:\TT\DATA and C:\TT\POSTING each to xxx.old
Copy DATA and POSTING directories to C:\TT\