HD Help!!

Hi Everyone!
Ok i spend 8 hours a day behind a computer at work and a good amount of time behind one at home.. For a time as far as computers went i knew next to nothing.. I could send emails like a champ though
Just recently i took an A+ certification class offered at work.. Very helpful.. Learned a whole lot.
With my new found knowledge about computers i thought id try to assemble my own.. All went well as you can see. Im typing this message on my new set up.
Have only one problem though.. Which goes as follows..

Im running Duel HDs. The HD i had for my old system has WinME on it. Its an ATA100 20G HG.. Unsure of the maker. My first system was Gateway <Ghasp>. It came with the system.

The new HD i got is a Maxtor UltraATA133 40G. This to be my primary HD..

So heres the problem..

When i boot up using the old HD (ATA100 20G). I go into My Computer and can see the other HD (Maxtor). Can transfer data back and forth no prob. Everything is peachy there.
When i boot up with the newer HD (Maxtor ATA133). I go into My Computer and there the old HD (ATA100 20G) is showing up as a removable device. (Has an icon that looks like a floppy drive with a big "MS" on it). Wont let me access it. Says to insert a disk in the drive.

Im stumped here.

At the moment i have the Maxtor ATA133 set up as the Primary and the ATA100 set up as secondary. In order to transfer data i have go into bios and set the order in which the system boots and swap em. Not a super inconvience but id like to be able to swap data and have the extra storage without having to edit Bios every time.

Both HDs now have WinME on them.. (Origanally the Maxtor had 98 on it. Still had the problem with 98.)

I went into Start>Settings>Control Panel>System>Device Manager.. There it recognizes the Drive and says its working correctly with the latest driver.

Though it might have been a problem with weither the drive was the Primary or Secondary on the IDE controller. So i setting them both up visa versa and no luck..
Also tried going through all the combinations on the back of both HDs.. i.e. Master, Slave, Cable Select.. No luck.
Went to Maxtors website and had no luck there.

Does this sound like its just an incompatibility issue between the two HDs? ATA133 Vs. ATA100?
Did i miss something? Anyone have any Ideas or suggestions or am i just out of luck?

Sorry for the long post.

Serious replys only please!
Thank You in advance!
Fractional

Unfortunatly i've tried them on both buses. For the life of me i cant figure out why it only works unidirectional.
I fear my last choice might be to wipe it but then again if that doesnt work i would have gone through all the saving/transfering/fdisking/formating of data for nothing.
Definatly something to consider though.
Thanks for the response.