My PC is loud

My computer is really loud, what can I do to make it quieter? I have 2 case fans (front & rear), one on my p4, and one on my geforce 6600GT. (Yes fail for p4, i know)

Would a new case help? And if so, please recommend me a decent case, preferably in aluminium or something. Should I replace the fan on my p4 as well? I'm not looking for a absolutely silent PC, just something thats bareable, and may be to leave on overnight for torrents. I already tucked it under a shelf and its still pretty loud.

Find whatever's the noisiest component (most likely your CPU fan if you're using the stock Intel P4 ones, since they are shit) and either replace it or insulate/isolate it. Zalman Flower coolers are excellent for CPUs. Repeat until satisfied or until the cost gets too much. You can get insulated cases, but they are worse at heat dissipation (whatever insulates sound insulates heat too) - you should be removing the source of noise first before moving onto muffling that noise. You can probably get away with just replacing the CPU, GPU and case fans with quieter ones, and maybe the PSU fan too.

Actually it might be the HDD's. I had a problem like that once and it was my Western Digital HDD that caused all that noise. The solution was to screw the disk more solidly (I usually only screw the hard disks on one side).

My cousin has the exact same case as me, and his PC's also loud, but not as loud (his mobo only has connector for one case fan), so i'm thinking of getting a lian li v1000, they seem good and all, but does anyone know how quiet they are?

I may replace the intel heatsink if the new case alone doesnt do the job.

any other recommended cases?

oh, and i just checked my drives by copying a file from one to the other, they're both very very quiet compared to the fans.