Try switching power management to Home/office. Then run some programs like window movie maker, photoshop (if you have it), photo explosion (if you have it), etc.
Then check your properties again. Usually, power management setting and source of power (AC or battery) determine CPU clock speed. At least for Centrino. Don't know much about AMD64 YET
Go to amd.com and find the power now dashboard. Win XP can't always tell you the correct speed. Dashboard can. I find CDex to be a good way to busy up the processor. Encoding MP3 with it usually will use every available cycle, and it is well behaved enough to share with other processes, so you can interrupt it.
It will run at lower clock speeds with the default "eMachines" power profile if the CPU isn't being heavily utilized. There are two options to "fix" this. One is to simply set it to "Always On", or "Home/Office Desk". Both of these will cause it to run at its full clock speed (2.2GHz, but faster than a P4 3.2) when plugged in. The other is to install "PowerNow!" in Win2k compatibility mode. This will add a tab to the power properties to allow you to manually control the dynamic stepping of the processor speed on AC or batteries.