i actually had the same problem as your having when i 1st got my board last week ....came to find out that the tnt card is very...very picky as to how it is seated into the agp slot....try resetting it a few times...and it will finally boot up....at least mine did and we have pretty much the same system specs....
SYSTEM SPECS...
tbird 900
chrome orb cooler
tornado 1000 case
196meg pc 100 ram
abit kt7-raid
SB live x-gamer
riva TNT... junk card
Tekram 390-f SCSI controller
plexwriter 12/4/32
ultraplex 40x reader