Saw on here that one way to fix it is to set the game's process affinity to a single core.
[url=http://www.gogwiki.com/wiki/Blood_2:_The_Chosen_%2B_Expansion#Known_issues]http://www.gogwiki.com/wiki/Blood_2:_The_Chosen_%2B_Expansion#Known_issues[/url]

Usually I'll crash when exiting a multiplayer server, however when I switched the affinity to a single core it didn't crash.
Special thanks to Korell for helping me out with this stuff.

The following fix will add a shortcut to your desktop that loads a batch file which will run Blood 2 under only a single core.

THE FIX(Windows 7 Tested):
For those who have tried multiple other fixes, don't run any of the Blood 2 files in any compatibility mode but make sure they are all running as an administrator. Make a batch file with the following commands but using YOUR Blood 2 directory:
@echo off
cd "C:\YourBlood2Folders\"
START "Blood 2" /affinity 1 "C:\YourBlood2Folders\BLOOD2.EXE"

Place the file in your blood 2 directory or wherever you see fit (other than desktop). Right click the batch file and create shortcut. Place the shortcut on your desktop, right click it, and click properties. Click the "shortcut" tab and click advanced. Finally, Check "Run as administrator" and press ok.
Now Blood 2 shouldn't crash when you run it through that shortcut (I HOPE)!

THE FIX(old):
First of all don't run blood 2 in any compatibility mode but do run it as an administrator. Though Windows 98 compatibility mode automatically sets the affinity to a single core; for some reason the game will still crash.
Go to start menu and type in taskmgr. Run that as an administrator. Right click Blood 2's process in task manager. Set affinity. Uncheck all but one core.

Why all the quotes? Can't use just use one set around the full path?

start /affinity 1 "C:\GOG Games\Blood II\BLOOD2.EXE"

Oddly enough, that doesn't open the game O_O. For some reason, the one with all the quotes does though.An alternative is this:
start /affinity 1 "" "C:\GOG Games\Blood II\BLOOD2.EXE"

Btw if you want to see that "new problem" with the batch file i'm trying to make, you have to run the .bat as administrator also.

Tried that out and it still comes up with the error. Here's a screen shot of the error to be more specific. Thanks for the help btw.

Ooh, could it be the working folder? Is there a blood2.rez file in the same folder as the BLOOD2.EXE file? If so, maybe you need to have a CD command in your batch file so that the working folder is changed to your Blood 2 installation folder.

Yeah it's in the same folder, how would I use this CD command?

Got it working! Here's the final batch file:
@echo off
cd "C:\GOG Games\Blood II"
START "Blood 2" /affinity 1 "C:\GOG Games\Blood II\BLOOD2.EXE"

Excellent! So it was the working directory, then, as adding in the cd command fixed it.

Yeah that's what fixed it. Thank you so much :).