Thanks again everyone. Problem appears to be solved although I am not 100% how or why. Yesterday I ran a system restore from many months ago. It took an extraordinary amount of time (like an hour) but when the PC eventually restarted it went through a sort of chkdsk routine on my second HD, which I never use. It locked after about 10 sectors and I rebooted. Same again. Soo.. today I cleaned that second drive thoroughly and now Add/Remove progs works fine. I can only assume that it was interrogating the second drive (F
for some reason.