i recently purchased oblivion goty edition and have lost disk 1 but i have disk 2 with shivering isles i thought it would install reg oblivion but no so what do i do?

You could http://www.zenimax.com/contact_email.php and ask for a replacement copy.

this is contacting bethesda no?

Not really, we are just volunteers who dont actually represent Bethesda. You want to contact them http://www.gamesas.com/eng/contact.php