USB to PS2 adapter.

[DaOld Man]

Ok, I bought one of those Dell OptiPlex Gx520 small form factor PC's from arrow direct.
Fast shipping and a very decent price.
My nephew Adam (who lives around 150 miles from me in Louisville, Ky), said he would like to upgrade his Arcade cab (Adam's Arcade, my second arcade cabinet built for him).
So I thought this could be a good Christmas surprise for him, but since he lives so far away, it would be really neat if he could just swap it out with the PC that is in there now.
He will be in to visit his dad and I thought I would give him the PC, all set up and ready to go.

But here is the reason for this post.
His cab is using a keywiz keyboard encoder with a PS2 interface, but this new PC has no PS2 connectors on it, only USB.
No problem, I thought for I have a USB to PS2 mouse and keyboard adapter in my junk box.
Hooked it up to a ps2 keyboard and mouse, plugged into a usb port on the PC and tried a few games.
On all emulators but mame, I am seeing this problem:
When holding a direction key (left or right arrows), the character moves until I hit any other key, then after a few frames the character stops. All other action still continues, it's just as if I released the arrow key, even though it is still pressed.
The character remains stuck until I release the arrow key and press it again, then the character continues movement in the direction of the arrow key, until I hit another key, then a repeat.
This becomes a big annoyance when you are moving and firing at the same time.
The adapter is a Black Box USBPS2.

Has anyone had any experience like this? I wonder if the keywiz will act the same as the keyboard does? Im betting it will.

It would be simple if I could swap out his keywiz to a USB one, but with the distance between us it would be a chore mainly because the I/O connector on that keywiz had the IDE cable pin arrangement, and since GGG don't offer that model anymore, a complete CP rewire would be necessary. (Or at least a rewire at the keywiz).
(I thought that IDE cable pin arrangement connector was a great idea BTW, cause you could use an old IDE cable to wire up all your switches, making the keywiz very easy to swap out if it fails.)

[05SRT4]

Does the Motherboard have any extra PCI slots open?

Maybe something like this PS/2 PCI Card or like it depending on what PCI slots they are.

So you don't have to switch anything out on the arcade.

[CCM]

I had the same issue with an ipac when I upgraded my PC.   I ended up buying a new USB ipac.   How old is your nephew?   Swapping out a keyboard encoder is pretty simple work, as you well know.   

[DaOld Man]

I ordered a dell 3000 from arrowdirect.com, wound up costing me 17 bucks inc. shipping. Used code dell50 to get 50% off.
This pc is supposed to have PS2 connectors so Im hoping this will be the best fix.