XP - VISTA - WINDOWS 7...
MTU LOVES XP!!!!!!!!!!!!!!!!! We have XP systems ourselves, so we will continue to test and support XP for the foreseeable future.
VISTA IS BAD NEWS!!!!!!!!!!!!!!!!!! Worst decision Microsoft ever made, and they and Wall Street KNOW IT. To the extent that WIndows 7 code will run on Vista, we will continue supporting Vista. Some of our Beta Testers have Vista and MTU has 2 Vista systems, but we don't see any "special" fixing being added just for Vista after about a year or so (don't hold me to that).
WINDOWS 7..... seems to be Microsoft's saving grace. IF.... they don't mess it up like they did Vista. So far, ALL MTU software products run on Windows 7 (we have a Beta version in-house). So far, Hoster 4.09 runs on it. We are ready for the Windows 7 roll out, which appears will be Sept-Oct. 2009 (Sept. 1 goes to the OEMs who make the computers we all buy). I just heard that Microsoft now says they will allow "downgrade to XP" from Windows 7 into 2011. That's music to our ears. XP is THE BEST for Professionals today.
Hoster Lyrics Sync...
Gentlemen, we hire human programmers, not robots, and I am human also (Pres of MTU).
Humans make mistakes. I made a BIG one by hiring a "consultant" last year... who already knows Hoster very well from years of working for us as needed.
1. He was to replace our "CDG Render" display with a new Direct-X player... FAILED... and lyrics sync was adjusted 18 times before I finally let him go and we reverted back to our tried and true CDG Render code.
2. He was to replace our Video player with a new Direct-X player... it too FAILED. My senior programmer took our older video player and made it appear in our new "Show Display", which does take more RAM and a faster processor, but makes it many times easier to set up a show.
3. He was to upgrade our audio player to handle 2+ audio streams for crossfade... FAILED! This set Hoster back almost a year on getting crossfade working and released. FYI: Hoster 4.09 DOES allow playing 2 audio streams so the core "upgrade" is done and released. We now begin this week (after 4.09d releases) on adding the fade ramps, timing, etc.
We threw out months of his work in half a day as we reverted back to the 4.07 code, but retained the 43 new-upgrade-bug fixes our other staff had added that became 4.08. Yes, it was a setback, and yes, 4.08 had a bad sync problem as it turns out the consultant had "tweaked" our sync code to try to make his "audio mixer" work with Hoster's lyrics.
That my friends.... is why we came out with 4.09 to fix the 4.08 sync problem. It did, but it had a
few quirks of it's own, so we released 4.09a... 4.09b... 4.09c... and Lord willing, tomorrow we'll release 4.09d. It's summer time, Beta Testers are swamped, some are sick with Cancer, some have retired from doing Karaoke shows so the QUANTITY (not the QUALITY) of testing has suffered. Each person tests in their own style. I carefully choose a diverse group of users - technical/non-technical - fast/slow computers - XP/Vista - (you get the picture) to insure as best I can that we get a good cross-section of testers.
We are adding a few new testers to our group right now as some of our great testers won't be able to return to testing due to health issues taking all their focus. It's very real life and we do the best we can with the resources available.
So, there you have my treatise on our sync problem and Windows versions. I truly believe that 4.09d is stable for everyone. If not, we'll do a 4.09e.
We are already underway on 4.10 with crossfade, which is why we can't do 4.09, 4.10, 4.11... 4.12. 
Dale mentioned 4.20. Yes, there are a number of powerful features we have in mind that probably should advance the version by a full X.1X increment. But that's fodder for another treatise.