Stefan - 1:02 am on Jun 24, 2010 (gmt 0)

on the main site there is no link to that folder..

Not sure what folder that is, but if there's only one link to your site from his spammy site, it probably won't make any difference. Just be sure to not link back to him.

will it have a negative effect on the normal links placed on that site?

Yeah, they might all be worthless.