upgrading from Win 98 SE to Win XP Pro

I have purchased more OEM Win XP Pro disk to “upgrade” my current network. BUT, these disk do not offer a “upgrade” on the drop down menu. ONLY shows new installtions. When I try to continue it acts as though it is installing but, hangs up after 30 to 45 minutes. I have uninstalled all virus proct. and nothing extra is loaded into memory. CAN ANY HELP???
Thanks