My woes began several years ago when I purchased 2 Dell Dimension 4700s for myself and my wife. Mine was to be used for FS and picture editing, my wife's for general day to day stuff. Little did I realise how much hassle was in store when it came to upgrading my computer to keep up with constant hardware upgrades.
The specs for both comps were as follows .... Intel P4 3Ghz with Hyperthreading, 512mb memory, 160Gb Hard drive and an X300 PCIe graphics card. DVD rewriter and a 305watt PSU all packed into the case below.

All worked fine for a couple of graphics card upgrades and added memory. The fun started when it came to upgrade from an X800 graphics card to the X1900 which would require a new PSU. I purchased an Hiper type R 580w PSU and squeezed it into the Dell case, little knowing the potential for trouble.
**** CAUTIONARY BIT ****
I was lucky as most Dimension 4700s' have a standard ATX setup so a standard ATX PSU will fit without causing any problems. MOST DELLS DONT USE STANDARD ATX SO UPGRADING A PSU CAN CAUSE FATAL DAMAGE TO MOTHERBOARD AND PSU. Dell to ATX converters can be purchased online. I in my hurry to upgrade didn't know this and wasn't warned by Dell's tech department that this could be the case ........ Once again I state I was lucky.
It became evident over the next few months that cooling and lack of power from the PSU was causing the X1900 to fail so drastic measures were needed to solve the ongoing problems.
It became evident that the current dell case was not going to be big