I'm not sure what you mean by compliant and supported, but here is what I have from the release notes of various versions.
LV6.1, NT4SP3, XP (first version with XP Support?) LV7.1, NT4SP6, XP So, the current version of LV (7.1) will run on NT4 with Service Pack 6 and XP. The earliest version of LV the NI announced XP support for was 6.1. I'm not sure if earlier versions would work or not. I'm not sure what NI's policy is on selling old versions, but since the current version works on NT, it probably isn't an issue.
