One person says yes and another person says no. In a way they are both correct.
Even if you do install on XP, because the minimum requirements do not include XP, if you have problems and need support you will be told that Vegas 11 is not compatible with XP if anything at all and you will not get any help. SCS will not support anything outside of the requirements for Vegas 11 and they do not have to.
It does not make any sense to even try to install on XP!
If you want to avoid problems AND get support, upgrade to Windows 7.
Honestly though, how often do you need to contact support? In over 10 years of using this software, i've contacted support 4 times. Once to ask about getting the MP3 plugin for SoundForge XP 4.5, once to reset the activation counter for one of my serial numbers, and twice to transfer old licenses to someone else.
All four of those incidents would have been handled even if i had done an unsupported installation.
As an official Contrarian, I still use it because everything runs great, I know it probably nearly as well as MS support, and see little reason to heave it overboard. I run Avast for antivirus and ZoneAlarm. This PC is on 24/7 as it also is a server.
I've said I will keep XP until some program I truly need won't run on it. Uh-oh. TurboTax has said this is absolutely, positively the last year. Well, we'll see.
Mozilla Firefox is still supported on XP but Internet Explorer and Google Chrome are not. How much longer for Firefox? I have struck new versions of other software as well that won't run, but one can always stick with the old versions with possible consequences.
I use XP for audio and video input because there are no later drivers for my hardware. I also use XP for web browsing and trying out utilities, to reduce the likelihood of internet nasties biting and incomplete uninstall crud from accumulating on my main Win 10 machine.
I recently had a case when I was swapping disks around for some reason, which now escapes me (a frequent occurrence these days!), when a disk mysteriously reverted to 32 GB capacity instead of 2 TB. After fumbling around with disk partition software of various brands to no avail, the disk suddenly came good but another disk went down to 32 GB. After searching the web I came across a nifty utility called "HDD Capacity Restore", which fixed it in no time flat. (It just changed some flags on the disk.) Unfortunately it won't run on Windows after XP and won't work on USB drives. Hence, another reason to retain an XP machine - running old but useful utilities.