I just went through and deleted the "backup" entry for Abes Oddysee in VGE and it got me thinking about why they sometimes show up.
I was reading on the MSDN forum that legacy applications often require the creation of a customised game definition file that provides detail about the game. [url=http://msdn.microsoft.com/en-us/library/bb173447(VS.85).aspx]This MSDN page[/url] says: "Be sure that bstrGameInstallDirectory matches the folder of the legacy database; otherwise, the legacy game-system will assume the game is installed multiple times, and will not override the legacy entry"
I'm just wondering if perhaps this could be the reason that some people have 2 entries. I never install software to the default locations because I have an organisational scheme I've used since windows 3.1 and I'm too much of an old fogey to adapt to the modern style you kids are into. As well as changing the default install location, I also often rename the install directories, in the case of the oddworld games, I rename them to add the prefix "Oddworld n - " (n being the number in the series) so I can tell at a glance what order they're in because thats the sort of stuff I often forget.
Could changes like that be the kind of thing the GDF can't adapt to and that causes the duplicates?

I thought the dupes were a case of the GOG.installer creating a custom entry, but Games Explorer also picking up an entry.
For much the same reasons you have two listings in Add/Remove - Programs&Features.
One of the staff here did explain it at one point, but I can't find the thread.

Cheers Oldski!
I knew it was listed here, I think I'll go take a nap to restore my searching ability.

Just so you know: I don't get duplicate entries for both Oddworld games in win7, so it seems like MS changed the default behaviour.

Damn, I thought I'd hit upon something cool there! Oh well, thanks for the info anyway