I was wondering how I can use the BartPe app from a usb drive, which i already setup to fix a boot.ini problem on a netbook. I have used BartPe before but not in this way and not without a cd. Any help would be appreciated.

Insert the USB drive into the netbook.
Boot the netbook.
When booting enter the BIOS setup.
Modify the BIOS such that the USB drive will boot before the hdd.
Save the BIOS changes.
You should now boot to BartPE.

If your BartPE is old, it will probably not recognize your netbook's hdd. You will need to add SATA drivers to it. See this link for help on how to do that.