Title says most of it. My old HP keyboard wore out, or at least the 'E' key was on the way out. It was also generally getting sticky and harder to type on than I liked.
Of course, I wanted a full mechanical keyboard as a replacement. I can spend 10+ hours per day on the PC. This is hardly unusual these days, I think.
Also of course, I wanted a PS/2 keyboard that worked with my old Trendnet KVM - a TK-400, to be precise. This is a circa 2001 unit that has been working fine for me for years, and since I have 3-4 PCs hooked up at any given time I really did want to keep it.
Anyway, after much hunting and pondering of a Das Keyboard, I foud the Adesso MKB-135B. This is a fully mechanical keyboard with Cherry Blue switches, n-key rollover, blah blah but more importantly, it's a PS/2 native unit. It comes with a USB adapter, and has a built-in USB hub that needs a USB connection to work, but first and foremost it's a PS/2 keyboard.
It's available from Tiger Direct in Canada. I took a chance and purchased one, and it works fine with the Trendnet, no issues at all.
So, there you go, a fully mechanical PS/2 keyboard that works with KVM switches. They're not expensive for full mechanical, either. If you need it, get it, you won't regret it.
This wasn't going to be a review, but since I'm writing anyway:
Capsule review: The keyboard is solid, looks nice, and has a good feel. Not too noisy for me. Go read the other reviews on this unit if you want more details. There are even videos on YouTube with noise tests etc.
Noise review: Everyone worries about the noise. I would say that it is a bit louder than my old HP membrane, but not as bad as you might be led to believe. The HP is not silent - no keyboard is - so the overall noise is about the same with the addition of the little clicks. Certainly the clicks add to the noise, and the spacebar is louder, and you tend to type faster so it seems noisier. But it's not hideously loud, IMHO. (I do work in a solo office, though, so your co-workers might disagree if you work in an open-air or shared office.)
Weight: Heavy for a keyboard. Makes my old keyboard feel like a toy. Won't slide.
Bonus: There are hookups for a 2-port USB hub, a mic and a headphones jack right on the keyboard. They are hidden out of sight so they don't make the unit ugly. You obviously need a USB hookup to make the USB hub work, but I don't think it's required to make the keyboard itself work.