HP Dx2300, E2140 is powered by 1.6Ghz Pentium Dual Core, 512 MB DDR2 667 memory, 80 GB of hard disk, and comes with 3 years of warranty. It also comes with an activated and licensed Microsoft Windows XP Pro.
I find the system very stable. I leave it on for days without shutting down, and have no worries that it would overheat or anything, as the cooling system seems to be very good. As well as very quiet too. Unlike my two other computers where you could hear the hum of the cooling fans, HP Dx2300's cooling system is very quiet. Except for the few a few seconds at boot up, where the cooling system speeds up, but then eventually becomes quiet.
It has a built in speaker that plays not only beeps, but even mp3s, and you can hear your videos. But the volume may not be too loud, so you might consider buying good headphones or speaker systems.
This microtower has relatively good expansion. It is not very stylish in its casing, but it makes up for its usability. I've heard that it is as good as Dell's Optiplex line.
Dx2300 is also Microsoft Office 2007 ready. That means you'll have a 30 day trial version installed, and you just have to buy the license to activate it.
Here are some expansion slots if you plan on upgrading its features:
Inside the Microtower
1x PCI Express 16x Lanes
2x PCI Express 1x Lane
2x DDR2 memory slots
4x SATA connectors (2 free) PSU Connectors
1x mini Molex
1x 4-pin 12v Aux
1x 24-pin ATX
2x PS/2 ports (keyboard/mouse)
1x Serial port
1x Parallel port
1x VGA (video)
4x USB 2.0 ports
1x 10/100 Ethernet Jack
3x Audio Ports (Line Out, Headphone, Mic In)
2x USB 2.0
Headphone and Mic In audio jacks