So, I have a T7400 Precision Workstation that came with 8 GB of RAM - Filling DIMM slots 1-4.  Works fine.

I ordered this kit:<ADMIN NOTE: Broken link has been removed / replaced from this post by Dell>

Installed it in DIMM slots 5-6.  Memory Info in the BIOS sees the DIMMs as being installed but reports the total RAM as still being 8 GB instead of 12 GB.

Windows Vista x64, when going to properties of the System, says 12 GB, but when looking in Task Manager, only shows 8 GB.

Any ideas?