forwarding domain to wordpress install

hey guys,
been searching through wordpress.org for a few days now and cant quite find the answer to my problem…
i have a host through godaddy which i currently use for site1.com (not a word press site)
on the same host i have now installed wordpress to use for another site, under the directory, site1.com/site2/wordpress (wordpress install)
this install was working great with no errors until i tried forwarding and masking the new domain i purchased to use instead of site1.com/site2/wordpress, now i get all kinds of access denied and invalid uri errors. plus nothing looks right anymore.

what is the best way to send my domain (which is registered through a diff. company than the host btw) to my word press install under an older domains directory.

i know its a little confusing, hopefully i made it clear enough, but i also do not want to do just a forward bc when ppl come to the site say mysite2domain.com (forwarding to site1.com/site2/wordpress) i do not want them to see the other site and this long path when switching between pages…

thank you, hope you all can offer some kind of assistance!!!