Alright, here is the problem, with all the mods installed from the guide I have beaten Planes.
Every time I close the game it says the game has crashed, this is not really a problem as this has no effect to the gameplay itself but I'd like to know why because the pop-ups get rather annoying.
Here are my hardware/OS specs:

Microsoft Windows 7 Home Premium 64-bit
Intel Core i3 M370 @ 2.4 Ghz

I have the same issue. Older PC and Windows 7 ultimate. Not sure whats going on.

as far as i know its about windows7. but it has absolutely no affect on gameplay.

same problem

Win 7/64 on a Toshiba L455 laptop

minor annoyance, worse since mouse gets "lost" for a bit

I have a lot of games that crash on exit in Windows 7 x64. In fact, I believe it's over half of my currently installed games that do this, and some other applications do it too. So I figure it's a problem with Win7.

I've got the same problem, running Win7 32bit.. Doesn't affect gameplay but I'm curious as to what's causing the error.. I wonder what the executable tries to do when you exit the game.. hmh.

-Edit below-

Well... heck. After running around the internet for some answers.. I took a gander at my event log, and found out the crashing component on my computer was something called ntdll.dll..

After reading a helpful forum on some random website, I tried something very basic: I turned my antivirus program off while playing Planescape: Torment... The game did not crash anymore while exiting. (avast!)

Could someone else try switching their antivirus off and start/exit Planescape? It'd be nice to know if it makes any difference for someone else :)

Here is what worked for me.
Somebody said they only need the first one "Emulate Heap"
It's easier than turning off your Antivirus each time.

Download & install the Compatibility Administrator from here http://www.microsoft.com/download/en/details.aspx?id=7352
Run the 32bit version.
It will start with New database(1) [Untitled_1] highlighted.
At the top, click on Fix.
Name the file to be fixed ( I put PST ) Then browse to your Torment.exe file.
Click next, to the compatibility mode screen. Ignore that & next again.
At Compatability Fixes, tick the ones you want.
EmulateHeap
IgnoreCRTExit
IgnoreFreeLibrary
were enough to stop it crashing on exit for me.
You can click Test Run to make sure.
Then next, then Finish.
Then Save.
Then right click on New Database(1) & install.

The fix detailed by olnorton (10-1-2011) worked for me on Win 7 64-bit Pro. I just needed the Emulate Heap fix. Thanks, man.

Complete awesomeness! Thanks so much, olnorton.

As with muun, I only needed EmulateHeap ticked and it exits without error.

Running Win 7 Ultimate 64-bit

I've been using VirtualBox to run Torment in WinXP SP3 with hardware acceleration really low and its been running pretty smoothly (seldom does it crash). I saw this post so I figured I'd see if I could get the old save I had on win7 working again. So I was able to exit the "Midwife hut" successfully (which seems to be one of the worst rooms to enter and exit and I was previously not able to exit at all). Unfortunately it crashed after I tried to re-enter and exit one more time.

Anyhow, I think either method can get us through one of the best told games of all time.

- " In enduring, grow strong. "

The fixes outlined above worked, but there were a few deviations between the instructions above and what one actually has to do. They were close enough and worked so my thanks to those who posted.

DrT

What did you have to do differently?

Your not running any extra software with this.
Win7 runs a shim for PlanescapeTorment.
All this does is add Emulate Heap fix to the default FUSBadApplicationType1 fix.
Or you can go into applications & disable FUSBadApplicationType1, and then you are just replacing a fix that does nothing for one that does something.