Giorgio,
I rescanned the external disk and now apparently works great. It took more than two days to build up.The catalogue size is 115gb from this is a lot even because I have other five disk to catalog, I can't keep all them on C .
Since I'm not going to use the catalog everyday can I store it on an external hdd?
Yes.
How can I move the catalog from the actual position to the external hdd?
1) Quit Photo Mechanic Plus
2) Move the catalog to the external drive.
3) Open Photo Mechanic Plus
4) Open the Catalog Management window (Catalog->Manage Catalogs...)
5) Click on the "Locate Existing Catalog..." button and use the dialog that appears to find the catalog on the external drive.
That should do it.
Though, now that you've done this, the proxies will never be used and don't need to be there because in order to use the catalog, the drive will have to be connected, and if it is connected, then your images will be online while you're using the catalog. And you'll also lose the ability to search for images on that drive when it is disconnected, because the catalog won't be available.
-Kirk