my machine is suddenly extremely slow

[Frédéric Bron]

Using Fedora 18, KDE 4.10.2 on x86_64 laptop with kernel 3.8.11-200
and nvidia proprietary drivers.

I have two hard disk. One SSD with / and swap and one hybrid with /home.
Recently, I remarked extremely long times (>60 s) to open some
programs like firefox or dolphin, the latter being the most critical.
I suspect disk access to slow down the machine as this happens when
the processor is nearly idle.
What can I check? Can I check the hard disks, how? Could it be something else?

Thanks for help,

Frédéric