MBP Running Hot & Slow

Question

MBP 2008, 2.53 GHz Intel Core 2 Duo, 4GB, Snow Leopard 10.6.8
Over the last few weeks I've noticed frequent spinning parasols and what seems like generally slow performance. However I was truly shocked when I worked on my wife's cheapo Windows 7 Toshiba, it was lightning compared with my MBP.
Now the MBP is running very hot with the fan frequently screaming, even when CPU is 40% idle (which I think is relevent).
Does anyone have any suggestions, or where I could look for the problem?

Answer 1

Disconnect all wired peripherals except keyboard, mouse, and monitor, if applicable. Launch the usual set of applications you use when you notice the slowdown.
Step 1
Launch the Activity Monitor application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, press the key combination shift-command-U. The application is in the folder that opens.
☞ If you’re running Mac OS X 10.7 or later, open LaunchPad. Click Utilities, then Activity Monitor in the page that opens.
Select the CPU tab. Select All Processes from the popup menu in the toolbar, if not already selected. Click the heading of the % CPU column in the process table to sort the entries by CPU usage. You may have to click it twice to get the highest value at the top. What is it, and what is the process? Also post the values for % User, % System, and % Idle at the bottom of the window.
Now select the System Memory tab. What values are shown in the bottom part of the window for Page outs and Swap used?
Step 2
Launch the Console application in the same way as above, and select “kernel.log” from the file list. Post the dozen or so most recent messages in the log – the text, please, not a screenshot. If there are repeats, please post only one example of each repeated message.