How would you begin to fix something like this?

SYMPTOMS: 1. When upright, the computer fails to boot. The power light comes on, no video, no drive checks. 2. When on its right side (motherboard facing up), the computer fails to boot. The power light comes on, no video, no drive checks. 3. When on its left side (motherboard facing down), the computer boots fine. The power light comes on, video works, drives check, and the computer boots.

ATTEMPTED FIXES: 1. I unseated the 2 512MB DDRs and re-seated them. I unplugged all the PCI cards and AGP card, reseated them. 2. I unplugged the 2-channel IDE cables, and reconnected all the IDE drives. 3. I checked all the case fans, motherboard fan, and cpu fan. All working, no bearing failures. 4. I cleaned all the drives and motherboard with compressed air to remove dust.

ANY IDEAS? I'm at a loss. Given that it only boots when in a certain position (computer on its side, motherboard facing down), I'm lead to believe its either shorting out or there's a bearing failure in a fan, HD, CD, or DVD drives.

There's 200GB of HD, 1GB of DDR, 56X CD-RW, 4x DVD-RW, SB Audigy EAX, and a 64MB DDR ATI Radeon that I'd like to save from this if it turns out to be a motherboard problem.

Any ideas on what might cause this? Any help or thoughts would be appreciated at foremank[@]starband[.]net ...Thanks!