Why can't I open e-mails with attachement on this particular computer?

Answer 1

well u forgot to say what windows version
what program your using to get your emails
whas the error message
etc etc
if its outlook express u need to goto tools/options/security and untick do not allow attachements.

Answer 2

i don't know why exactly, becasue you didn't specify enoght information.
But probably because somewhere in the settings it is configured not to allow such emails.