PC Freezing

I recently had to put together a new computer using an ASUS motherboard (P4P800S) Intel Celeron 2.0GHz processor, 512mb ram, 80gig Western Digital HDD and a new power supply. THe motherboard has on-board audio and LAN connections and I am using an S3 video card. After loading Windows NT 4.0 workstation when I try to double click on any desktop icon or insert an auto-run cd the computer freezes. If I try to install Windows 98 SE the computer freezes on the Starting Windows for the First Time Screen? Help!!!!!