Dell Inspiron 530 Core2Quad q6600 minitower cheap overclocking - success!
Bottom line: for about $25 you can get your 2.4GHz running at 3.0GHz for a rock-solid quiet quad-core machine (which is BTW not supposed to be overclockable due to a "plain vanilla" motherboard, weak PSU, restrictive case, etc). Read on.
All IMHO and YMMV (and you luck is also YMMV), of couse. Not all CPU's are overclockable, not all components are fault-free.
After a lot of reading and thinking I found the following. No need to upgrade 380w dell PSU nor your minitower case. No need to remove the CPU bracket from under the motherboard nor lap your CPU/heatsink . No need to use "high-performance" thermal paste. You do need to upgrade the CPU heatsink. That's it.
My choice was Arctic Cooling Freezer 7 Pro ($16+SH at ewiz.com here ). Fits right in into (quite small) 530 mini-tower case.
OK, here we go:
1. If you don't have one, hunt for a Dell Inspiron Quad-core w/ Q6600 on outlet.dell.com. Look under "Core 2 Quad - 2400" or "Core 2 Quad-core - 2400", somehow Dell has two choices for the same processor in that drop down menu. Look for mini-tower form factor.
This is the most time consuming task and it is YMMV, but you can do it. I got a q6600/4Gb RAM/500Gb HDD for $295+SH (with a 10% off coupon popping up here and there on SD). My PCs "flaw" was two small scuff marks on the bezel. That's it! Again, YMMV.
2. Order AC7 Freezer 7 Pro from ewiz.com here .
3. Get to a hardware store and buy 4 metric screws M3-.50 x 16 and a bag of small hex nuts 8-32 (you'll need 8 of those). It will set you back about $2. This will allow you to remove push-pins from the AC7 cooler and use the screws instead to mount AC7 to the Dell-standard backplate.
4. Open your 530, and using a philips screwdriver unscrew the stock HSF (heat sink fan) assembly and discard/give it away.
5. Take the CPU out and do the easy tape mod described here . I used a small piece of office scotch tape. Put the CPU back into the socket. Clean up old thermal paste with a napkin from the CPU heat spreader.
6. Remove push-pins from your new AC7 as described here . You'll be using screws now. I like that approach because a) you don't need to take the mobo out and remove the backplate holding the stock HSF. b) The bolt-thru setup takes the stress of holding heavy heatsink assembly off of the motherboard itself.
7. AC Freezer 7 Pro is supplied with the thermal paste applied. Use it! No need to remove it and replace with "better" paste. Also, no need to lap the CPU/heatsink (polish the contact surfaces making them perfectly flat using sandpaper).
8. Use your new screws with two hex nuts as spacers to screw the heatsink into stock backplate. It will require some effort and accuracy, but you can do it. Use a long shaft flat screwdriver to tighten the screws. Don't tighten the screws all the way down. Leave about 1/8 inch between the tension legs and the motherboard.
According to Prime95 (v25, x64 version) my system runs at 2993MHz with no errors for several hours now running various tests, max temp was 59C, idles around 25-29C.
Needless to say I am loving my 530 now. Hope this guide helps.
P.S. You can put Windows XP x64 on that machine. I run it just fine. I found all the drivers so let me know if you are interested hearing about that.
UPDATE ABOUT SCREWS: Recently with my second 530 I discovered that to mount AC7Pro you can use small standard PC screws usually used for mounting CD/DVD drives. Not the screws with larger thread used for HDDs. No need to buy any screws at a hardware store. No need for spacers/washers as those standard screws have quite large heads. The correct small-thread screw is depicted to the right (below).