Drivers for Hard Drive Not working Properly

My dilemma is I have a hard drive that was evenly split into two partitions.
I tried to reallocate the partition. For example I was trying to make my
drive c go from 50gb to 75gb and reduce the d drive from 50gb to 25 gb and
all it did was create a third drive so I reversed that. Now whenever I turn
my machine on it wants to load the hard driver. When I say yes you can no
longer see the d drive so I ignore this, but everytime the system asks the
same question. Another problem is every time I try to use a thumb drive or
external hard drive I get the same dialog about loading a driver so I can
never install an external drive. Any suggestions for a fix.