2007 MBP 15" palm rests working as mouse click

Have the same problem on my late-2007 17". Like you, have never been able to track the cause (although to be fair it's also never quite bugged me enough to take it in to get it looked at).

Not exactly a helpful reply, I'll admit - but at least it's not just you with the issue...

NCW said:

So I have recently noticed that the area on either side of the trackpad on my 15" 2007 MBP are acting as a left mouse click when a very small amount of pressure is placed on them. When I say small, I mean the amount you would put when typing normally, so really nothing at all. It's not that big of a deal, but can get annoying when I end up highlighting and deleting something I have typed. Has anyone ever experienced this happening before? Not quite sure what might be causing this. Any help would be appreciated!

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Even though you are out of warranty i would just get it checked by a genius and maybe its just a simple fix.

This may or may not help, but when my trackpad on my 2007 17" MBP went completely haywire (either didn't click or just touching anywhere made it click randomly) the problem was suprisingly the battery. Alot of the 2007 MBPs suffered from expanding batteries, which would literally burst their seems.

I flipped my MBP over and literally the thing was bursting. The battery is in such a position that any swelling causes internal pressure on the trackpad from underneath making it behave eratically.

About £100 later (ie a new battery), my MBP was as new ....well, almost, it's still a 2007 model.

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....you can test this by taking the battery out, whilst still having the AC cord still plugged in and seeing how the trackpad behaves then.

If the problems resolved, then you've found your cause.