ther is no difference between an ATA-100 and ATA-133 as far as motherboard compatibilty with hard drives. ATA-133 is fully backward compatible with ATA-100. You could plug an ATA-133 hard drive into an ATA-100 mobo, or a ATA-100 hard drive into a ATA-133 mobo and either would function just fine. Its all the same plug/connector/cable.
I dont think ATA-133 hard drives are that common, as most companies have moved on to developing SATA.