I forget whether you're using 32-bit or 64-bit Windows...although SampleTank is compatible with Windows 7, it's 64-bit only.
64-bit Windows. So in theory it should work with Reaper unless Reaper doesn't support 64-bit plug-ins. But that still doesn't explain why loading Sample Tank by itself crashes. Maybe it wants more memory. The crash report is a Windows message, not a Reaper message, something about Windows trying to find a solution, but says it can't.
Just for kicks, I should probably try installing these IK programs on the computer I'm using now (the one in the office) so I don't have to run to the back room to try suggestions as they come in (I don't do e-mail and avoid web surfing on the studio computer).