I dunno anything about your currency equivalencies but the cheapest decent computer you could get as far as I know is:
a 17" Acer monitor or cheaper if U can find - $240 USD
computer with a gigabyte or asus motherboard with 5.1 sound and ethernet on the motherboard to save tons of money and with at least one fast pci-express slot. I'd suggest a low end dual core AMD X2 like a 3800+ or the one higher model. Either socket AM2 or 939 is fine, each are about the same price but since 939 is older, the processors are a hair cheaper and so are the motherboard and there's almost no difference in performance. 1 GB of DDR ram (of DDR2 for socket AM2) may actually be cheaper in 1 stick than in 2 of 512 so check both options out. Get whatever size hard drive you want but whatever motherboard you get will almost definitely take SATA drives. I actually have 120, 160, and 300 GB SATA drives in mine hehehe

And if you really want to save money, get a do it all drive that can read and write CDs and DVDs otherwise I always prefer having a reader only DVD/CD ROM drive seperate from a writer cuz I think writer ones are slower. And what would a computer be without a Coolermaster Centurion Case with a window and some cold cathode neons lol

Oh yeah and the graphics card! So your motherboard should have a pci-e slot so I'd suggest a Geforce 6 series card. They're around $150 USD now I think. My Nvidia BFG 6600GT is fast enough to run anything and it's pretty much $160 anywhere now. You could also probably go with a couple models down from that and have pretty good performance. Nvidia 7 series are too expensive and not good enough for the price if ya ask me
I just had a computer built for a customer of mine with all the above specs except no monitor and 512 MB of RAM for $575 USD.