Ghostdog74, that was exactly my point about regular expressions being potentially too inclusive.

By matching only valid characters (or avoiding invalid characters) you reduce issues later.

Example, to search for test followed by any number(including zero) of any character (excluding spaces and \ characters), followed by a .iso:

sed -i.bak 's/test[^ \]*\.iso/test0123-new.iso/' test.vmx

As we only want to exclude spaces and \ characters, this is shorter than my previous example, while still only finding valid matches.

EDIT:-

If you want to match a full stop you need to escape it (using \) EG: \.

that's why my own preferred method is using fields and not worrying about regular expressions and its always the last field i want to change. well anyway, OP has got a solution, so it should be fine.