Really slow Tecra M2



My Toshiba Tecra M2 has suddenly become unbelievably slow. It's not related to the o/s or any software because the problem is evident as soon as the machine is turned on. In both Windows and Linux under idle conditions, the CPU load is about 25%. Even the simplest task consumes 100% CPU load. Both operating systems take about 5 minutes to boot and about the same to shut down.

Before I start running any diagnostics (which are going to be slow!), has anybody experienced similar problems on any laptop? Any suggestions where to start troubleshooting?

Thanks
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