The new HP Compaq dc7900 Ultra-Slim Desktop PC  provides business-class desktop computing in a notebook-size form factor, sacrificing very little to give you the best of both worlds: a world-class workhorse with a small footprint.
The first feature that stands out about the HP Compaq dc7900 Ultra-Slim is its size. At roughly 2.5 inches wide and 10 inches square, it’s just about the size of a ream of paper. But small does not equal sluggish: Hewlett-Packard maximizes the desktop’s processing power with an Intel Core 2 Duo processor, backed by a maximum of 8 gigabytes of SO-DIMM RAM, using Intel’s Q45 Express Chipset and integrated Graphics Accelerator 4500, which supports DirectX 10.
And if you’re anything like me, you can’t have enough USB slots: There are eight of them, six on the back and two on the front. For those who have soft phones on their desktops, headphone and microphone jacks are conveniently located on both the front and back of the computer. A pair of PS/2 ports, a VGA adapter and an RJ-45 network adapter port round out the available connections.
An ultra-slim computer can’t hold everything, so HP moved the 135-watt power supply outside the machine, placing it along the cord. The dc7900 Ultra-Slim is Energy Star-qualified and EPEAT Gold registered, with up to 87 percent energy efficiency. But best of all, there’s one less fan inside the box, which means it’s quieter.
Given how small the dc7900 Ultra-Slim is, I was a bit concerned that it would be difficult to use — but I was wrong. A few turns of a thumbscrew and the top slides right off, clearly exposing the two SO-DIMM slots, the processor and the slim DVD combo slot (notebook size). Sliding out the DVD writer with LightScribe drive exposes a curious — and well-designed — drive cage that nicely secures the 2.5-inch hard drive into its connector without forcing it.
For mounting, HP has a quick disconnect hardware option for walls, the underside of desks or the back of monitors. There are four mounting holes on either side of the desktop to attach it to the hardware.
Some sacrifices have been made to accommodate the dc7900 Ultra-Slim’s size.
For instance, there are no parallel or serial ports. To be fair, it’s been a long time since I’ve needed one — these days, most printers connect over a network or via USB — but there are still legacy applications and external RS-232 communication devices that just won’t work on this machine. There’s also no media card reader, although you could buy an external one and hook it up to a USB slot.
The dc7900 Ultra-Slim offers few options for expanding its capabilities. The mini PCIe slot is useful only for a wireless network interface card or a TV tuner (usually factory installed), and there’s no place for an advanced video card. And with only one bay available, there’s no room to add a second drive for RAID 1 reliability.
If you need these features, the dc7900 Business PC series includes the larger Small Form Factor and Convertible Minitower models.