ACT4A allows you to move ACT out of your LORD directory.  Before doing
this, run your old ACTCFG and UNINSTALL it.  Then run the new ACTCFG from
your new ACT directory and INSTALL.  

Or just edit your 3rdparty.dat file like this:

PRE-UPGRADE:

ACT.EXE * C:\DOORS\LORD
`0Across the Tracks

POST-UPGRADE:

C:\DOORS\LORD\ACT\ACT.EXE * C:\DOORS\LORD
`0Across the Tracks