Emails go to OE>tools>options>maintenance and click on Store Folder to find out its location. Write this down Go to Control panel>Folder options>view and put a dot into Show hidden files and folders and untick Hide protested system files (you will get a nag message but ignore it. Now make your way to the location you wrote down for the store folder and copy the whole folder to another drive. OE>File>Export>Address book to somewhere. You may be better off if you can buy or borrow a usb drive to put these items on. When you get your system fixed you reverse the above processes.
Copying data to external drive in similar way.
For the future, if you fit a second drive, you can designate your store folder to be on D drive and keep all data on D drive. Use Acronis TI to back up working C drive.