New computer...

I am thinking of buying lots of parts myself, and putting together a new computer, but I stumbled across something on ebay this morning and was unsure about what to do. I don't know too much about price ranges of computer parts etc, which is why I came here to ask you guys.

I found this >> http://cgi.ebay.co.uk/Custom-built-gaming-pc-in-Thermaltake-case_W0QQitemZ300014484651QQihZ020QQcategoryZ179QQrdZ1QQcmdZViewItem self-made computer, which a guy is selling, and what I want to know is, is it worth the £600 price tag it has been given?

620 British Pound = 919.336 Euro
919.336 Euro = 1,183.22 US Dollar
919.336 Euro = 1,329.72 Canadian Dollar
919.336 Euro = 8,454.04 Swedish Krona

(inc. P&P)

*EDIT*

This is my current computer:

(CPU1) Intel® Pentium® 4 CPU 2.40GHz @ 2411MHz (Gigabyte Technology Co., Ltd. GA-8ST800 mainboard) , 120.91MB free
(HDDs) 115GB, 41.4GB free
(VGA1) RADEON 9200 SERIES (128MB), 1024x768x32, 85Hz
(OS) Microsoft Windows XP Professional (SP2), 7h 25m 48s uptime, 4d 23h 51s uptime record