I'm looking to install the trial version of vCenter operations Manager. Can this be installed on vCenter 4.1? I can only find a download for vCenter 5.0?
Which version of vCenter Operation Manager do you have ?
Look this release notes of version 5.0
vCenter Operations Manager supports VMware vCenter Server 4.0 Update 2 and above, managing hosts running ESX/ESXi 4.0 and above.
Information about deploying vCenter Operations Manager is available in the vCenter Operations Manager Enterprise Installation and Configuration Guide. The guide contains information about all requirements and procedures to set up vCenter Operations Manager and also addresses prerequisites.
Note that vCOps is a vApp that contains 2 VMs, it isn't installed on the vCenter server.
That said, it should be fine with 4.1