Couple of questions first:

1 - Can you check the partition?  It might be corrupted.
2 - Can you install the DDO drivers without reformating and partitioning?  I
know the Maxtor drives let you do that.

If you can just reinstall the DDO drivers then that should solve the
problem.  If Seagate is like Maxtor's installation program it might have
promoted you to make a boot disk with the DDO drivers on it, if you have one
of those try that.  If you still can access your hardrive then it could be
that your Hard Drive's partition table or Master Boot Area/Record (MBA MBR)
was somehow corrupted.

Someone else might be able to give you better help, I recommend calling
Seagate if everything else doesn't work.  They are a pretty reputable
company from what I hear.