Macbook pro has slowed considerably and ...

My Macbook pro has slowed considerably and spinning beach ball appears lots recently.

After I installed 10.5.7 it started happening. When I open anything including system prefs and apple apps the ball appears. I'm on 10.5.8 and it seems to be either as slow or slower. Startup is a bit faster now, but it'll go to the beach ball before I even do anything remotely intensive on the system.

My computer is almost 3 years old but I don't install any weird software on it and have 30% of my system disk free. I'm an audio guy and use logic, pro tools and generally keep my computer clean.

I've tried starting another user account to check if its my original user that has the issue, but thats just as slow too.

Please help...
Thanks

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