How do I know which version of MDAC I am running?

A. Check the following table :-

MDAC version      Msdadc.dll      Oledb32.dll
------------------- --------------- ---------------
MDAC 1.5c          1.50.3506.0 N/A
MDAC 2.0            2.0.3002.4 2.0.1706.0
MDAC 2.0 SP1     2.0.3002.23 2.0.1706.0
MDAC 2.0 SP2      2.0.3002.23 2.0.1706.0
MDAC 2.1.0.3513.2 (SQL 7 / 6.5 SP5a) 2.10.3513.0 2.10.3513.0
MDAC 2.1.1.3711.6 (Internet Explorer 5) 2.10.3711.2 2.10.3711.2
MDAC 2.1.1.3711.11 (GA) 2.10.3711.2 2.10.3711.9