Isn't it just the fact that we're talking about DDR (Double Data Rate) memory? Like the memory runs at 166 MHz, but the data rate is 2 x 166 = 333 MHz effectively? If you're still not sure, download CPU-Z and check the Frequency under...
Do you really mean "...there is response..."? =)
Have you looked in the device manager if anything is wrong? Also check System Information.
Maybe the last owner disabled it in BIOS? Dunno if it's possible though.
I'm currently looking for a low cost laptop, I've found a CM and a PM model:
CM 360 1.4 GHz
512 MB RAM
60 GB HD
X600 64 MB
µ$ Windows XP Home
Price: 6000 SEK = €640 = $777...