I was looking to replace my system and I was thinking about a 64 bit one. Are there any disadvantages to 64 vs 32? Are my old 32 bit programs able to run on 64? I have a copy or Ubuntu 64, but I was unsure of the rest of my programs. I know nothing about 64, but thought that the AMD Athlon dual-core 64 bit CPU and motherboard would be pretty fast. Thanks!