[BNM] JPGs won't open

[Adurman]

I've got a selection of JPG images that were 
taken on a digital camera, mucked about with 
briefly in PhotoShop CS on a Mac and then 
copied to a CD and then given to me. I can 
open them fine on my Mac but can't in Windows 
XP. They appear in Explorer as JPG files but 
won't preview and I can't open them. Each 
file name begins with an underline but I've 
tried renaming them and it makes no difference.

Before anyone says 'look at them on the Mac' 
I need them on XP so I can stick them on the 
web.

It's probably something obvious but I know 
nothing pf graphics on the Mac.

TIA

A.