if the old machine is still working cheapest way is to network the machines or if you're not comfy with that to use a usb stick
if only the hdd works you need (as ethel calls them ;-) a USB 3.5" caddy (typhoo?) or enclosure
http://www.google.co.uk/products?sourceid=navc lient&hl=en-GB&rlz=1T4GPTB_en-GBGB295GB295&q=u sb%203.5%20hdd%20enclosure&um=1&ie=UTF-8&sa=N& tab=wf
how much you spend on an old disc is up to you ...
if it's less than 100Gb I wouldn't spend much unless you intend to upgrade it at some time