What ATA do I have

I have tried to find answers in these forums but here is just too much advertising to get anywhere.
I hope someone(s) here will help me even if you seen my problem a 100 times.
I am not an expert at computer repair but I have fixed a few over the years.
Right now I got this gateway 2000 that I want to use for playing games on. It was working when I got it but hard drive was having software issues, and being over 10 years old I thought it best to replace the HD. So I bought a new WD1600 IDE or EIDE (not sure). I knew about barrier limitations to access larger HD's, but Western Digital EZ-DRIVE utility is supposed to solve it. But it did not. So now I am looking for a solution.

After many hours searching & learning, I now know that I have a promise ultra 66 PCI card controlling the HD. But I read somewhere it can only support up to 128 GB. So I thought about putting a promise ultra 133 PCI card in it, but this idea oped up more questions which I am here now asking.

The cpu is an Intel Pentium III 600 Mhz, Tabor 3 BX motherboard uses an Intel®/Phoenix BIOS, Made in 09-12-1999 it came with windows 98 installed.

My question is how do I find out what ATA speed the motherboard uses?
And, would I benefit from installing a 133 card or should I buy a smaller HD and use the 66 already in the computer?
Or is there a better option?

Thanks