XPS 420, Intel Core2 Quad 9650, Two Vertex 2 180GB SSD's in Raid 0, Two 1 TB WD Cavier Black 7200 RPM 64 MB Cache SATA III Drives, 8 GB DDR2 SDRAM PC2 6400 at 800MHz, Seasonic X Series 660 Watt PS, XFX Radeon HD 6990 GPU, Windows 7 Pro 64 bit
Optiplex 990 MiniTower, i7 2600, Seasonic 650 Watt X Class Gold Power Supply, Win 7 64 bit Pro on Two OCZ Vertex 3 MAX IOPS SSDs in Raid 0 array on SATA 3 Intel headers, 1 TB WD Cavier Black 64 MB Cache SATA III, 16 GB DDR3 Crucial RAM, soon to replace stock video card, NEC USB 3.0
I also tried several things to quiet my fan down. I pushed it against the side of the desk; that helped for a few seconds, but then the noise was just as loud. I tried tipping it (carefully) and noticed a small difference in the noise level. I even opened it up and used a can of compressed air to spray the dust out of the inside.
Finally, I put a heavy dictionary on top of the tower to dampen the vibration; it was heavy enough that the noise and vibration were almost unnoticeable.
After 2-3 weeks, I finally removed the dictionary and the fan has been at a reasonable level since. If it gets noisy again, I'll try the heavy dictionary first before calling Dell.
--Slightly off the topic, I just had my Lite-On CD-Rom drive replaced (it wasn't reading CD-Roms any more). Dell's service (after the phone "web" I had to go through to get to a tech) was quick, and the replacement was done 2-3 days after I called them.
So I had a great experience with their service.