Prior to Windows 95 the preponderance of Windows programs were 16bit. Seeing as 16bit programs are not compatible with recent versions of Windows one can be reasonably assured that they are not in that vast pool of legacy applications.
Hand in hand with 32bit Windows came the registry, which is where most applications stored configuration information until relatively recent times.
To the best of my recollection, I have not seen an application or utility hard coded to C: since Windows 95. But I would be interested to learn of the actual examples which support your assumptions.
Most code was written for internal systems. So even if you don't encounter them there are plenty of hard coded paths including drive letter in plenty of systems.
Hand in hand with 32bit Windows came the registry, which is where most applications stored configuration information until relatively recent times.
To the best of my recollection, I have not seen an application or utility hard coded to C: since Windows 95. But I would be interested to learn of the actual examples which support your assumptions.