Tif file from PC user causes problems

[Jane Sprat]

I received the TIF file from a pc user as an attachment in an email. When I open it (by either double clicking on it or opening GC and using Open and selecting the file), then use the Select icon (just below the Hand), go to Picture and hold the list open, 'Resolution down thru Colors, Median thru Duplicate, and Full Screen thru Play' are grayed out. If I copy that file as a TIF, and open this new TIF file, the same results occur. BUT, if I use this original TIF file in GC to create a JPG, and/or create a JPG and save to a TIF, then open THIS new GIF or TIF file, everything is NOT grayed out. WHY? Is this just with a TIF file or would ANY file from a PC user cause this problem? Jane