Windows 7 Pro definitely. I've been using Win 8 & 8.1 for a year now and it's basically Win 7 with a ton of Window dressing. You can run it like Win 7, but you'll spend half your time working around their bloatware.

Going into 8.1 is a dicey risk - if you believe that VegasPro 2014 coming out in September 2014 is going to be mostly tailored to W8.1, but that is not a given.

Win7Pro is a sure bet for good reliability for VegasPro 8, 9, and sometimes VegasPro12.

Windows 7 64 bit Ultimate.

I have a copy of Windows 8 but I'm still using Windows 7 64 bit on my main machine. Windows 8 is geared towards touchscreen applications. All my main programs are not.

WIndows 8.1 is my vote. Have no fear. Runs fine. I would not think that anyone is developing new software to run it's best on Windows 7 ... why would they? Of course, you could play it very very safe and opt for Windows XP and use Vegas 8.0c ... and buy a new video camera that runs tape .. and hey why not put a floppy drive in for safety .. I could also sell you a great back up drive called a Syquest !! BUT I will admit I keep a supply of candles in the house just in case the power company blacks out.

Full disclosure. I own stock in Microsoft.

Built a new Haswell 6-core editing machine a few months back and re-installed (from scratch) my Windows 7 Ultimate on it. Runs fast and reliably with Vegas 12 /770. Do not remember a hiccup with this combination for the last 3 months.

In order not to become regarded as totally outdated by the grandchildren I have secretly put a Windows 8.1 on my new i7-4500u laptop - and after some cursing and installing the Classsic Desktop - that machine runs Vegas 12 /770 with 3.rd part plugins and FX'es rock stable as well.

Conclusion: If it were not for the grandchildren, however, I would any time reformat the laptops disk and install Windows 7 on it:
The Windows 8 user interface solemnly assumes that its users are morons hardly able to do anything but clicking some icons and apps.

Vegas Pro v12 runs fine on my Windows 8.1 x64 machines. Overall, I like Win 8.1.

Full disclosure. I own stock in Microsoft.

Watch out, incoming!

Don't "upgrade" yet from Windows 8 to 8.1 if you have a Raid system. I run a Raid-1 system and my disks became inoperative after the download of 8.1 and right when the 8.1 installation started. I then had great trouble restoring the system because of my backup software (Acronis True Image) letting me down.

When you google for "Windows 8.1" and "Raid" you'll see that this combination is a problem. Maybe this is sorted out in the update to 8.1.

Lou

Just to play devil's advocate; I orderd my new system with Win 7 pro after asking the same question, then installed 8.1 as a dual boot for V12.

Some of us are still using XP 14 years after it's release, intend to keep using it for a long long time, and are even still installing some *new* XP systems. I have VirtualBox installed on my Win7 64bit laptop and still do most of my 'money making' work in an XP instance.

I suspect 7 will still be around and supported 10+ years from now too.

Win 8.1. We have 7 at work, my wife has 7. IMHO, the UI of Vista is better then 7. The UI of 8.1 (never used 8) is better then 7. 8 boots my machine, from power on to in account in 39 seconds. The new start screen is faster for running programs then the Win95 way that Win7 uses. The only issues I've had so far have been 3rd party issues (ie Avast! was crashing my machine when the monitor wakes up from power save & stopped Hitfilm Express from loading a new project).

Skip 7. You'll be glad you did. It's just a convoluted mess imho. Can't figure out what it wants to be.

Another vote for 8.1 - very fast boot up, very stable and solid. Windows 7 seems like a slug compared with Win 8.1. Booting to the desktop a huge improvement over Win 8. Win 8.1 on a touch screen laptop is amazingly fast.
Really grown to like 8.1 - both on PC and laptop.
Zero issues with Vegas 12 or Hitfilm - not one crash.

To me it would be more a question of what kind of GPU do you intend to use. If you go for a fast GTX570/580 then you need Win7 to run the older driver (296.10). If you don't or don't care so much about GPU acceleration or performance then go with Win8.1 and hope that Win9 will be finally a professional OS again with a free upgrade from the worst bloatware OS that MS has ever made.

My earlier comment about the release of VegasPro 2014 in September was meant to cover an issue - namely a GPU variant that would be enhanced in Windows 8.1 OS. Certainly depends on whether SCS will really intend to move that direction. AND if they can pull it off.

I run Win 7 on my machine...

You can look up my specs...

My machine boots from cold start to any program operating (such as Vegas Pro 12) in 88 seconds...

The real advantage is that its been doing just that for 4 years now...

My daughter had been using 7 for the same time period...

Now she uses 8.1 and loves it...

To each his or her own .....

Will...

Thank you everyone very much for your comments on this issue!

~Adam

Remember also that Microsoft is dumping Windows 8.1 for 9.0 in the very near future. Read it in the paper.
JJK

I haven't had to buy a new desktop in years so I run XP, V9c, and will continue to do so. It's bulletproof, no reason to "upgrade."

Oh, and yes, we have candles in the house. Matter of fact, here in Portland, Oregon we've had high winds and rain for two days, lost power last night, but WE HAD CANDLES, so we were okay.

Right now the house and PC are running on a generator. Power scheduled to be restored some time this afternoon.

"Newer" is not necessarily "better."

Remember also that Microsoft is dumping Windows 8.1 for 9.0 in the very near future. Read it in the paper.

They dump every previous version for the new one. Waiting to upgrade because a new version will be out "soon" means you never go anywhere.

Either way, look on e-bay for the retail versions. I got Win 8.1 retail with 32 & 64-bit disks for $85 with free shipping, new & sealed. Windows 7 should be similar. OEM's are handy but are starting to be system locked and retails seem to be no more expensive on e-bay. I'm not sure if Win7 retail includes both 32 & 64-bit versions, but I wanted a 64-bit OS, didn't want to spend over $90 & wanted retail. I looked until I found one that fit my requirements.

>> Win 8.1 is a hog of a resource that requires more power(ram) to run

Nonsense. Resource reuqirements for the past few verisions of Windows, that is, all versions after Vista, have gone down version by version. Win 8 requires quite a lot less resources than Windows 7. In Win8 Microsoft has also done some serious optimizations, and you can expect a measurable increase in performance.

When I upgraded my quad core box from Win7 to Win8 I got a 10-15% speed increase on multi-threaded apps.

First thing I do though is install Start8 on my Win8 machines though. I very rarely see the start screen.

>> you'll spend half your time working around their bloatware

Don't know who installed your Win8 with bloatware, but you should not continue to purchase software from them. Windows 8 is leaner, meaner and faster than Windows 7. It requires less RAM, runs multi-threaded apps faster and works identically to Win7 once you install the very lean and non-intrusive Start8.

People who claim Win8 is bloated compared to Win7 have never used Win8.