In Windows XP you can disable hibernation by doing the following:

1. Open Power Options in Control Panel

2. Select the Hibernate tab

3. Clear the checkbox for enabling hibernation

This doesn't work in Vista however because the GUI for Power Options has changed and doesn't offer the ability to disable hibernation. But you can disable hiberation in Vista from the command line if you use admin privileges. Here's how:

1. Press the WINDOWS key and type cmd into the Start Search box but *don't* press ENTER

2. Right-click on cmd in the Programs list and select Run As Administrator

3. Click Continue when the UAC prompt appears

4. Type powercfg -h off and press ENTER