-snip- I don't know where the blockchains are on my c: drive and I don't know how to find them. I also think it's likely that another set of blockchains might have been downloaded to my d: drive. My c: drive is now full to overflowing with data I can't find. -snip-
Maybe the following steps can help solve your problem.
On Windows 7, begin by clicking on the Windows menu. Then click your username from the right-hand menu. Windows Explorer should show a folder containing other folders such as Contacts and Desktop. Another folder, AppData is hidden by default. It can be shown by selecting the Organize -> Folder and Search options menu. From the View tab, click the “Show hidden files, folder, and drives” option, then click “OK”.
Windows Explorer should now display an AppData folder. Double click it. Then enter the Roaming folder, where the Bitcoin folder is contained. -snip-
Having found the default data directory, we can now copy it. Be sure that Bitcoin Core has been shut down and is no longer running. -snip-
Next copy the renamed bitcoin data directory to a destination of your choice. This can be the same hard drive, an external hard drive, or a removable medium -snip-
At this point your system contains two more or less identical copies of the data directory. Assuming there were no issues with the move, the original can now be deleted. -snip-
Windows users can create a shortcut that uses the command line option datadir. Doing so directs Bitcoin Core to use, not the default data directory, but the one given as a parameter.
Begin by right-clicking on the desktop and selecting New -> Shortcut. Browse to the location of the Bitcoin Core executable (C:\Program Files\Bitcoin\bitcoin-qt.exe) and click the OK button. Next, add the command line option datadir, using the path to your data directory.
Double clicking the newly-created shortcut will direct Bitcoin Core to use the new data directory.