OK, lets examine your PC in pictures. I will number each picture and explanation, so if you want to comment, please
DO NOT QUOTE ME FOR THE SAKE OF WASTING SPACE!
1. This is your PC with CPU cooler removed,
pay attention to the line of yellow "things" called mosfets (transistors)
Dell deigned its cooling system so that it will cool them as well, that is why there is a shroud (green box over CPU), if you did not use shroud the overall system is not effective, and to the worst of this, those mosfets might overheat and melt - the end of your motherboard.
2. This is how your original PC was looks like with old CPU cooler and shroud, am I correct?
3. So this is the original shroud which you can not use any more since you have now new tower CPU cooler, am I correct? Did you get new shroud as well?
And another larger picture of ORIGINAL shroud
Pay special attention to the part on picture where the wire is coiled, this part directs air onto those mosfets - now the gruesome news, you probably know this already or would be thinking about it.
THIS IS NOT EXHAUST FAN, BUT AN INTAKE FAN!
This fan blows fresh air over mosfets and through CPU cooler, into the case, this is old unpleasant Dell design, I have the same on the PC I am typing this, XPS Gen3, so I know!
4. This is the part you should have, new shroud for your tower CPU, if you have it already, please tell me where the fan is blows, where air is directed, inside the case or outside (exhaust). Unfortunately I have "dirty" pictures.
And another view
And last one, clean but small, but you got the idea
5. This is original 5 pin/4 wire fan for 4700 http://cpufans.ecrater.com/p/5156787/dell-fan-dimension-4700-g5883-n4399?keywords=G5883#
6. So, some information about CPU intake fan, please correct me if I am wrong
The fan is not a standard 92mm x 25mm fan. It will either be 92mm x 32mm or 92mm x 38mm and should have a special 5 pin connector that connects to the motherboard fan header. It will be mounted with rubber shock mounts (unless the original configuration has been changed). If the fan is changed the rubber shock mounts (called rubber screws) should also be changed.
I really hate proprietary Dell connectors...
7. So basically you need this part, I hope I am right (in terms of part number)
http://www.centrix-intl.com/details.asp?productid=1076 link provided for information only, have no idea where it is located.
And fan should blow inside.
8. Look at someone else drawing, it is telling me that you are not the first one to deal with this problem.
9. And now, here someone discussing similar problem, why should we think too much, lets see what others did in this case
http://www.overclock.net/t/570434/modding-a-dell-dimension-4700-for-better-airflow-56k-get-faster-internet-bro
[strike]10. Just in case verify is it your PSU shown below - we have to know you connectors and specs, just in case. Dell Dimension 4700 8400 350W Power Supply PSU (F4284 L350N-00)[/strike] Wrong power supply
[strike]Qty. Connector
(See table for picture and description)
1 24-pin ATX mainboard power
1 4-pin ATX 12V mainboard power
3 4-pin peripheral power (Molex)
2 15-pin serial ATA (SATA) power
1 4-pin Berg floppy drive power
1 6-pin PCI Express power
1 6-pin Dell P6 connector
Dell Part Number: F4284
Model Number: L350N-00, PS-6351-1DS
Compatible Part Numbers: G4265, U4714, Y2682, C4849
Compatible Model Numbers: L350P-00, PS-6351-1DFS, N350N-00, NPS-350DB A
[/strike]
So, please clarify ,my statements so I know where you are located in terms of your upgrade.
DO NOT QUOTE THE WHOLE THING PLEASE.