Tell me about this computer

I found this (secondhand) computer selling for 320 euros or 300 without the monitor. What do you think? Should I buy this computer or maybe it would be more cost effective to spend a couple hundred euros more and buy something better?
The specs:

CPU: Intel C2D E6600 2,40Ghz
Board: Asus P5B
Ram: 2x1Gb ddr2 667 (D9HNL chips) dual channel
GPU: XFX Nvidia Geforce 8800GTS (512Mb gddr3)
HDD: WD AAKS 320Gb sataII
Box: Antec Sonata III 500 piano black
PSU: Antec EarthWatts 500Watt PFC 80PLUS
Monitor: LG Flatron F900B crt 1600x1200, 0,24pitch + usb hub

Out of curiosity, what OS is it running?

XP I guess.

I would presume that the OS would be an additional cost, if it’s not specified. It may come with a blank/formatted HDD.