As always Coach Fred was too nice, so Coach Lemming will answer...
"Q: I confess -- I didn't ride very much during the winter. But I want to get in shape for a metric century on the Memorial Day weekend. Is there any hope? -- Calvin R."
You've got a lot of things to be worried about Calvin, but riding 65 miles two months from now isn't one of them. You aren't doing an actual century, but some organizer has duped you in to believing you are by eluding that anything that you do 100 of is a century. I know you want to complete the 100km in style, so you might read my century buyer's guide.
The first thing I would do is hire a coach. He'll help you with making riding less enjoyable and he'll state the obvious to you in so many words. It's obvious you are lazy and don't like riding your bike, a coach will whip your lazy ass and get you out there turning the pedals. Next thing you'll want to do is schedule your bike for a look over by a bike shop, last thing you want is a breakdown on this monumental ride. Now is the time to start stressing about which chain lube you want to use and what tires you will run, as well as deciding at what angle you will mount your aero bars. It's also the time to start looking at all the hype with sports drink and decide which one you'll want to drink in between the rest stops where you'll get crappy Accelerade and brown bananas. Also consider carbo loading, your taper, and your evening before meal, all very important on this super crazy long ride that a lot of people do every weekend for fun.
Or, if you don't want to do any of that, you can train with the secret training method of the grand poobah Lance Armstrong. Which is just getting out and getting your ass on your bike as much as you can before now and then. At the end of the day you might just want to ride 100 yards and declare victory on a "yard century".