Usually a laptop is set by default to power saving mode. This is also slow mode with reduced CPU performance. AFAIK, most all the power settings are in 'Control Panel>Mobile PC>Change Battery Settings'. You can set it to power saving mode and customize those settings if needed.
You can also save power by turning down your display brightness and setting the computer to turn off modems or WiFi devices if you aren't using them.
I would also check some reviews of that laptop to see if there are any comments about short battery life. My Compaq laptop is always on a power supply, so I don't recall what kind of battery life it has, but I also have it set for performance and I doubt it would last an hour on the battery.