I have an old PC, about 7 years, with an AMD 1250 MHz CPU.
First of all, in order for the installer to see the harddisk, it was necessary to write the following in a terminal:
sudo apt-get remove dmraid
and then answer yes, (I found this in a previous post).
Secondly, everything was hopelessly slow, and I was considering going back to Linux Mint 6 Felicia,
which worked ok.
After considerable searching and head scratching, I discovered that I could elimininate the lagging by turning off
the visual effects.
To do this, open the Control Centre/Appearance and click on behaviour/Appearance, then click on the Visual effect tab
and select None. (Note these menus are translated from another language and please forgive if they are
not the exact english menus, but they are easy to find).