Registry Error, No Access to Device Manager

A registry error occured when I restarted my computer. I
now no longer have an icon for my local area network,
although the network connection does works. I also can
not print via usb to HP Photosmart 7660 printer
(connection error). I have attempted to access my device
manger. It will open, but I can not see or select
anything. System Restore fails to work and I can not
replace any drivers due to the afore mentioned lack of
hardware access. Must I reload Windows XP to get Hardware
Device to work? I would appreciate any help. Thanks,
Joanne

DELL 4550, 2.56 MH,1G Memory, WinXP, SP2, HP Photoprinter
7660.