The term "Microsoft Data Access Components" is an unnecessarily complicated and techie-sounding name that simply means: "a bunch of free files from Microsoft that are needed to let your PC talk to databases".
Well, BigOven is a recipe database, and the way it's written, it requires the Microsoft Data Access Components ("MDAC"), which is a free set of database engine libraries that need to be installed on your computer. Most computers shipped after 1997 have these pre-installed; they also come with Windows XP, etc. So, to keep download files small, BigOven doesn't install these by default.
But over time, sometimes these files become corrupted, and it's good to update them every now and then. If you need them, they are free, you can download MDAC from Microsoft's site here.
Simply download the file called "MDAC_TYP.EXE" to your PC -- any location will do -- and then simply double-click on it to install the libraries. They are from Microsoft, they are part of newer OS's, and are perfectly safe.
What do you do if your PC still thinks MDAC isn't installed, or if your MDAC installation is corrupted somehow? (Symptoms of MDAC DLLs getting corrupted include the infamous "Parameter Incorrect" error message when data is being accessed.) The cause of this is that sometimes, poorly-behaving applications will muck with the way these files are registered when doing installs or uninstalls. If you believe MDAC is already properly installed (or the MDAC_TYP.EXE program tells you it cannot install the files), you might try running the MDAC Repair Utility, available here.