Hi Metroid,
Can see why your concerned, expensive bit of kit
BEFORE you make any changes create an IMAGE
most here use Macrium free.
If thats the version of Netframework your running, it is out of date
Program like this will perform a system check and if a newer version is required on install it WILL tell you.
Now back to your question,
have a read of this
.NET Framework Versions and Dependencies | Microsoft Docs
Im not technically minded in regard to the interdependancies between between NFW and Vegas etc
NFW is backward compatible so in theory you shoud not have a problem
So install the current version.
Note Vegas etc may have applied updates as well, possibly why your getting the error message as they require you to install a later version of something, this could include visual basics C++
(assume you have MS updates turned off - as a check select the LET ME CHOSE see whats there)
For your piece of mind Vegas/Adobe etc will likely have thier own support forums have a quick look at them search for netframework issues.
Roy