Vista not Wake Up after 2 hours Sleep

Hi everyone,this is my first post.
In the last two weeks Vista does not wake up after two hours sleeping, if it's less time there's not problem.
I have tried everything recommended and not yet solved the problem, e.g. unplugging mouse, keyboard, network,
changes in BIOS didn't work,drivers,System restore,unplugging a external hard drive that i've of 175gb,etc.

In the last months,sometimes(few),when i woke up windows my USB external hard drive was not in the list of available units,or if it was and i wanted to open a folder i get a message with "this folder doesn't exist".Then i believe that the problem is related to my USB...when i want to wake up the system,the USB is not recognized and by that windows does't wake up(because the folders don't exist).
I tried with the usb unplugged,disabled..the port to which it's connected disabled,uninstalled,allow the computer to turn off this device to save power,etc.

Now, i see only 2 options,uninstall the usb or format(although I've read that this does not help).
First i want to uninstall the USB "completely" but i've problems.In Device manager i uninstall the device but when i restart windows reinstall it again.If i uninstall the port too(usb root hub?) to which it's connected,the same,windows reinstall it again...then the question is if anyone knows how to completely uninstall the USB without having any trace of him in the computer.

People,I really need this option,i live in Spain,and here,it's very hot,i can't turn on the computer all times.
Sorry the long post but I wanted to explain it best,of course, if someone knows another solution to the problem would be welcome.

Cheers