Slow Mac HDD

[Superspeed500]

Hi,
I have an Macbook Pro 15 mid-2010 weakest config. The current Os on the computer is Mac Os X Lion. My Os is running extremly slow when the HDD gets heavily used. How can I lighten the disk usage? Will it help if I "Erase free space"? Or are there any other good solustions?

 

[B...]

Upgrade to an SSD if possible, or delete stuff.

 

[niteflyr]

More RAM

 

[Superspeed500]

Ok

Thx for reply. I have 4 GB of RAM and that should be enough. I think I will try an SSD upgrade.