This sounds like and IRQ conflict.
IRQ [Interrupt Reequsts] are commands the system uses to share resources.
IN the P.O.S.T screen [When the machine starts up] you will see the IRQ's and the devices installed and the IRQ's assigned.
Windoze decides what IRQ's are assigned, they cannot be modified.
However when you look you will see what devices are sharing the TV card - if feasable disable/remove those devices.
I Gave up on this years ago - got a secondhand TV instead.
PS Any one want a TV card?