Untested:

/<img \s+ id    \s* = \s* (?:'[^']*'|"[^"]*"|[-\w]+) \s+
          src   \s* = \s* WantToGetRidOfThis\.gif    \s+
          width \s* = \s* (?:'[^']*'|"[^"]*"|[-\w]+) \s* >/x;
[download]

Of course, you're probably much better off using an HTML parser.

Abigail