A friend on mine recently ordered -- on my advice -- a Vostro 400 tweaked to its highest settings with Windows XP Home, a quad core processor and 4 GM RAM. Fresh out of the box, it started up with the BSOD. After hours spent with tech support, we finally got a tech to the site with a new hard drive and video card. After installing them, he experienced exactly the same problem. He tried several things and finally called his tech support. I won't go into the gruesome details, but after trying to see if there was a bad memory stick, he discovered the problem only occured when all 4 sticks were in. After discussing this with the phone tech, I heard him say "Oh, I remember reading about that." Then he explained that 32 bit Windows XP will not handle 4GB memory, but that the 64 bit version will. We decided to keep the system with just 3 GB RAM in it.

My question is: Why does someone ordering this configuration not trigger and "incombatibility problem" response??