Has it always been that quick to drain?
Have you tried charging it at different outlets? Or tried a different charging cable?
The power saver properties are more for long term saving, like when to go on standby etc. If you are in a well lit room, take the brightness down, that will give you abit longer.
Only run 1 or 2 things at once, that will put less pressure on the CPU and memory, and will save battery life.
Alternatively, buy a new battery. You could probably find one by talking to Toshiba, or even looking on ebay.
There isn't much you can do to get more than that 45 minutes, seems to be a duff battery.