Did the 120mm fan fit into the case?
I bought my dell studio 435MT in juli 2009. It had already bios 1.1.2 installed, so no upgrade needed. Noisy at startup - 2 seconds - and after that there's a constant noise of a fan (when running idle). It's not loud, but it's there and you can't ignore it. I tried disconnecting the case fan (AVC DS09225...12H) and it's very clear that this one is causing the constant noise because the pc was absolutely silent when the case fan was disconnected. So I think Dell's only solution is the bios upgrade to stop the fan spinning at max rpm, but the fan itself isn't replaced.
I found this about the stock fan:
I found 3 other 92mm case fans that have +50cfm:
Zalman ZM-F2 plus: 2800rpm, 55.9 CFM, 36 dBA, http://www.quietpc.com/ie-en-eur/products/casefans/zm-f2-plus
Panaflo NMB-MAT 92: 2850rpm, 57 CFM, 35 dBA, http://www.heatsinkfactory.com/panaflo-nmb-mat-92mm-high-output-fba09a12h1bx.html
Scythe S-flex SFF92D: 2500rpm, 54 CFM, 33 dBA, http://www.heatsinkfactory.com/scythe-s-flex-sff92d-92mm-silent-fan---2500-rpm.html
I didn't try them yet.
I noticed that most of you have the HD4850, but mine was equipped with a HD3650 (256mb). I couldn't choose the HD4850 because the only option was the HD3650. I think that's the only change Dell made in the 435MT (at that time) . Maybe because the HD3650 is causing less heat?
I just had to signup to share my experience with the XPS 435MT.
Right from the start the fan was noisy under any sort of decent load. This reason is simple; it's the case, it is far to small and cramp to be adequate for an i7 chip.
The front of case should have a fan to throw some cool air into the case and out the back.
OK, so what did I change, well, pretty much everything in the end.
First off, I swapped out the case fan, with an Xilence Red Wing 92mm, which is a lot quiter than the standard fan, but doesn't move much air. Even this when running at max RPM is noisy enough to cause problems. But for me, it was the constant high to low RPM's that annoyed me the most.
So what next?
Next came the PSU swap, I tried a 600W OCZ PSU which is fully modular and a nice piece of kit - this wasn't to necessarily to quiten the noise, but made me feel better that the sytem had a decent PSU running an expensive i7 chip.
After months of being annoyed with the noise of the PC, I decided to swap it all out, and buy a new case.
I purchased an Antec 300 case, (brilliant case) which is quite cheap too and vastly, vastly superior to the standard DELL kit. With Two front fans, 1 side and 1 top, cooling was much better from the off.
In fact my idle temps went down from 50C to 40C, just by changing the case.
The system at this point was very, very quiet. So get yourselfs a new case... and or read on....
I kind of got the modding bug then, and went the hog, and bought a new motherboard, RAM, water cooling and case fans, SSD drive the lot.
I went for the H70 cooling from Cosair, using the DELL i7 chip, my temps are now down to just under 30C at idle and nothing more than 50C under Prime95 (100% CPU torture for an hour).
I cannot tell you how much better the system is now - it is quiet as a mouse and runs soo much better, I think the DELL mobo must be quite slow in comparison to a decent board.
If I have learned one thing during all this, is that if you really want a quiet / fast / stable system, then build one from stratch! It isn't all that hard if you take your time and you will have a system that is much more pleasing to work with.