I found the problem,i had 2 512MB.
1 was a CL2,5 and the other was a CL3.
the normal windows xp pro didnt have any problems with it,and my motherboard didnt eather.
but i`m happy the problem is solved!!
ps.it`s hard to get them 64-bit drivers.
but the athlon64 processor is running very fast on the new XP.