Cannot use P4Merge as diff tool

Hello,

I want to use P4Merge in unity PC version but I cannot choose p4merge in the list.

Unity->Preferences->General Tab. Had 3 drop downs available to me: External Script Editor, Image Application and File Diff Tool. For File Diff Tool, it had selected None, but when I hit that drop down to see my options None is all that was listed, so I couldn’t browse for DiffMerge.

I have installed p4merge with the common installer.
I am on Windows XP 64 bits.

I’m not sure if this will help, but when we setup Tortoise merge for ours (TortoiseSVN) Unity would only recognise the 32 bit installation, not the 64 bit installation. Not sure if you have a 64 bit version of P4Merge though.