WinXP SP2. Partitions = C, D,E,F,G

My C:\ drive with windows on it has become invisible!
Everything works fine but I cant see it in explorer nor when I click on my computer. Partition magic sees it ok. Partition not hidden.

When I right click on a shortcut on desktop and "find target", the C:\ drive suddenlly appears in a new explorer window.....but at the bottom of all other drives. When I open another explorer window besides it, C drive is not there!!

Happened after a registry clean using a prog called SmartPC.

Help please.