Check the file properties on W7. Does it have a "Warning this file came from another computer" with an "unblock" button? If so, you know what to do.

Alternately, open a command prompt (Start, type "cmd" then enter). go to the folder where the file is held (cd) and try an attrib on it, see what it has. You can remove with minus in front of the known attribs.

e.g.:
cmd <enter>
cd d:\images\example
attrib <myfile>.jpg

the output looks like this:
^ Archive only. If it has H, S, or R, then issue the appropriate command:

attrib -h -s -r <myfile.jpg>

(no news is good news)

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Maybe explorer tries to copy some data with the file (shouldn't, Explorer knows what to do with metadata, streams, security, etc), but a commandline copy command does wonders.

Make sure it is in mass storage mode. PC Suite is a bit funky.