Mouse option to switch buttons Disabled

Hi,

I restored my Windows XP Home Edition yesterday from the
Restore CD on my Dell Inspiron 5100 Laptop. Everything was
working fine till I noticed that I could not switch to the
left hand mouse.

I am using a Microsoft optical mouse with a USB port in my
Laptop. (The laptop has a synaptics touchpad on it).

The checkbox is apparently disabled and I cannot change
it. Before the restore eveything was working fine.

Please if anybody knows of this issue please let me know
of a fix.

Thanks

Nik