I Googled for 'MSDAORA ORA-1019' and got 207 hits.
I'm always unpleasantly surprised most people here refuse to Google, and others should do that on their behalf.
For sure, your combination of drivers is not certified on Windows 8.1.
Microsoft has never manufactured 100 percentage downwards compatible software.
Also Microsoft drivers have Oracle dlls hardcoded in their software, in the meantime the name of these drivers changed.
Oracle 9.1 was desupported many many many moons ago.
Your only hope is to use Oracle provided .NET drivers.
There are separate forums for .NET issue so your question is also 100 percent off-topic here.