Your E310 uses a standard ATX power supply. Just make sure the power supply you use has the needed power connectors (e.g. 24 pin or 20 plus 4 pin for the motherboard and 4 Pin Molex for the processor power).
Dell still uses proprietary motherboards but no longer uses proprietary power supplies on most of their desktops.
Dimension E510 with D925 CPU and Vista Home 32 bit
Home Built PC with Q6600 CPU - Vista 32 and 64 bit OS, Windows 7 64 bit RC1
Sonar 8 Producer DAW Software/Focusrite Saffire Pro 40 Recording Interface