I used to have a "CompareTo" on the context menu, this allowed me to select the first file to compare and it save my selection, I could then right click the second file and click "Compare".
I often need to compare files in different directory structures, so this was much quicker and easier then using the dialog that asked me to select both files. 
I installed winmerge on another (virtual) machine, but there was no "CompareTo" option on the context menu.  At first I thought I had gone crazy perhaps I had not been using winmerge at all or maybe it was removed from newer version or something, but I went back and checked the other machine again to verify it was in fact winmerge and checked the version, I used to have on this machine so I thought perhaps something didn't install properly so I removed and reinstalled but still no "CompareTo". 
Perhpas I was using some plug-in or something, any ideas how I get this option back?
- Kurt