that 1.7 P4 system isnt that bad... but TBH for a little more money you can get a lot more PC if you know what i mean

Rough price for you..
case £25
keyboard+mouse £15
motherboard £55 (inc sound/lan)
celeron 2.8ghz £70
512Mb DDR ram £50
17" monitor £70
CD rewriter £15
DVD re-writer £33
120GB HDD £50
Graphics card £35

Thats all pretty good stuff you could even save a few pennies here and there!
And obviously you wouldnt have to buy the dvd drive etc if you didnt want it.
you could just start iwth case, processor, mboard, ram, graphics card use your existing HDD, monitor, keyboard cd drive etc

CheeRS
Phil