So when i plug my external hard drive into my mac it connects for about 5 seconds then disconnects and doesn't reconnect, its formatted fat32 which is for both windows and mac and when i connect it to windows it works fine
Trust me when I say did to try to Reset Your PRAM? See if that helps and hold it down for three beeps then let go and let it boot normally. See if this helps, Good Luck.
Is your external drive 2.5" or 3.5"?
Did it come with an external power supply block?
If so, have you tried connecting it with the power supply providing power?
i think ive fixed it now, for some reason it stays connected with this usb which has two usbs on the end to plug into the mac, but it worked fine on a windows with just a single usb :S