Electric Sheep

I recently purchased a Dell Optiplex 745. It is an excellent computer with a Core2 Duo processor, 2GB of Ram, and a 10K RPM Raptor SATA hard drive.
My complaints with it are few but ones I feel strongly about.
The system arrived with an ATI X1300 video card, which is pretty weak sauce. Most users when tempted to upgrade it will be discouraged by the fact that there are NO PCI-E power connectors for higher end video cards. Added to this is the fact that the power supply itself is only 310 Watts. However as it was the sole factor keeping the WinSAT evaluation of my computer's performance low I bit the bullet and upgraded to an Nvidia 7900GS. I did this by splitting one of the 2 available molex power connectors and the reforming them into one PCI-E power connector via an adapter. So far the system has been stable, and the WinSAT score has jumped from 4.3 to 5.1.
During 1997-1999 Dell was infamous for putting similar keyed but incompatible power connectors on their power supplies and motherboards. As a result, if you just plugged a new ATX power supply in, you fried your board. Granted, this is not the case today, but if dell really wants people to not take such drastic action they could make the power supplies at least functionally capable of dealing with today's peripherals.

There are a few things you can do to make your system run a bit better.

Disable what you don't need (hardware)
Go into your bios and turn off the things you don't need. If you are not using your parallel or serial ports, turn them off! If you aren't using your integrated modem, turn it off!
However, I would suggest keeping a record of what you do turn off. That way you can have a first step in trouble shooting why a device isn't working.

Remove windows components you don't need.
Chances are you probably don't need MSN explorer.
in windows XP open add remove programs control panel and click on add/remove windows components. Then go through and remove what you don't need.
If you aren't using MSN explorer or Outlook Express, it is just taking up space and providing potentially security issues.

Update your dell firmware
http://support.dell.com has updates for just all about of their models. Most of the updates help performance, compatability, or reliability. Just make sure you don't lose power to the system during the update, and back up your data first.