Shuts down after ~10 mins running on battery

Question

For a year, my MacBook Pro ran fine. At the beginning of the previous school year (around September of '07), my notebook began to shut off before the battery was fully drained. Gradually it began to shut off sooner and sooner, until it finally shuts down not even ten minutes after unplugging it. The battery is only at around 90% when it kicks the bucket. When I try to turn it back on, the computer makes a noise as if it is going to turn on, but quickly drops dead again. Plugging it back into the power remedies this and runs normally, but what's the point in having a notebook if I can't work on it unplugged...?
Anyways, while at college I took my computer to the IT desk. Replacing the battery once didn't help, so we tried another battery... we must have done this four times with no avail. They decided to send my Macbook Pro to Apple and after a few weeks I got it back. For a few days it worked fine while running on the battery, but then it started malfunctioning again until I got back to square one. I didn't take it back to IT because I desperately needed my computer to work on assignments.
Here's my current power information, thanks to System Profiler:
AC Power:
System Sleep Timer (Minutes): 10
Disk Sleep Timer (Minutes): 10
Display Sleep Timer (Minutes): 6
Automatic Restart On Power Loss: No
Wake On AC Change: No
Wake On Clamshell Open: Yes
Wake On LAN: Yes
Display Sleep Uses Dim: Yes
Battery Power:
System Sleep Timer (Minutes): 5
Disk Sleep Timer (Minutes): 10
Display Sleep Timer (Minutes): 1
Wake On AC Change: No
Wake On Clamshell Open: Yes
Display Sleep Uses Dim: Yes
Reduce Brightness: Yes
Battery Information:
Battery Installed: Yes
First low level warning: No
Full Charge Capacity (mAh): 5076
Remaining Capacity (mAh): 4714
Amperage (mA): 818
Voltage (mV): 12563
Cycle Count: 33
Please help, this problem is very annoying.

Answer 1

There are several things you can do I understand.
1) Check the battery condition using a program like the widget iStatPro (free). If the battery health is less than 80% then Apple have a free replacement program for this.
2) Switch the machine off and disconnect the power supply. Remove the battery and leave out for several minutes - to allow complete discharge of all electronic components, I think. Then re-instal the battery, etc and restart. I'm not 100% clear on all steps in this procedure but it provides a reset which sometimes resolves problems at least temporarily.
3) Disconnect all peripherals and see how it works. One of these might be calling for more power than it should.
Neville