Should I buy this PC?

I've been looking for a new PC for less than £250! Crazy, you might say, but there are actually some quite good offers out there on t'Internet! I managed to find a PC for £239.95 with these specs:

• AMD Sempron64 3100+ processor (256kb cache)
  
• 512Mb DDR400 RAM
• 40Gb HDD (I also plan to add my 80Gb one)
• Onboard graphics*

*I chose to have the onboard graphics, and shop around for the best dedicated card.

I think I'm going to buy it!...