right thats it iv had enough my computer is almost dead

this morning i turned my comp on and it loaded ect like normal
i went to copy my dvd i downloaded yday and yeowch my comp crashed stoped
didnt do a thing it wouldnt even let me shut it down i had to do it by hand on the wall
now im running a the following system unbelievably
hewlett packard vectra ve
pentium prossesor 2
316 mb ram
windows xp home edition

now its extrely rubish as u may tyell by the description i just gave u

but i want to do a comp cheap and need sum advice

wats the best mother board but cheap ?
wats the best prossesor amd pentium ect?
and wat size hdd would be best for me
i download a lot and play a lot of games ect
and i dont want a system thats gonna crash every time it over heats ect

so thanx in advance guy but plz help with that stuff