My desktop is a windows 2000 machine and I have one database running under Oracle 8.1.6 and two databases running under Oracle 8.1.7. Just make sure you install the Oracle software into a different OraHome directory. In my case, I have C:\Oracle6\Ora81\... and C:\Oracle7\Ora81\... to represent the Oracle 8.1.6 and 8.1.7 versions.