Here's the steps I went through to start fresh on my 3650. It's working much better now that I reset it to factory settings and started again. If you're having memory problems like I was, this'll do the trick.
1) Take your MMC card out of the phone. I had a 128MB card with lots of stuff that I didn't want to screw up or spend too much time backing up (I usually make a copy of the whole MMC using an adapter for my PC when it has something important. It's faster and the files are more accessible.) The MMC isn't the problem, so let's get it out of harm's way. And, if you're like me and store your images, videos and messages on your MMC, this will also keep those items safe as well.
2) Make a backup using PC Suite. I used the Backup/Restore option at the top of the application bar to the left and made a backup of everything, and also used the Settings wizard at the bottom to copy just my "settings". Settings are your SMS server numbers, Email settings, and your Access Points. The cool thing about Backup/Restore is that you can do everything or just calendaring and contacts. For now, just do everything to be safe.
3) Use the PC Suite and copy all the stuff you want to save off your phone's memory. You can do a full-on backup if you delete something, but then you'll have to do a full-on restore to get to it, which isn't the idea. Go through and grab all the important files - I'm talking about just documents, images, sound files, stuff like that.
4) Do a reset. Type: *#7370# and when you're prompted for the lock code, type 12345. This'll erase everything and bring the phone back to its original factory settings. If you have troubles (like I did) take out the battery and re-insert it. It should work. If it didn't, well, don't blame me. :-)
5) Okay, now you've got to hook back up with the PC Suite. If you're using Bluetooth that means re-pairing your phone with your computer (it'll be easier if you use the same name).
6) Restore. First, restore the settings via the settings wizard from the file you created in step 2. Then restore the calendar and contacts. If you messed up you can restore some of the other documents, but I didn't do that.
7) Reinstall - Any apps that you had on your local phone will have disappeared, so you'll have to reinstall them from scratch. If something very important disappeared, go back to step 6 and restore everything.
9) Re-install the MMC. This isn't perfect, as I posted about before. Any apps you have installed will automatically reappear on the phone, but in the top Menu folder not where you last had them, and you will no longer be able to uninstall these apps using the Manager. Depending on the app, some registration settings may be gone as well and you'll need to re enter them. However, it's still better than losing apps or reinstalling everything from scratch.
8) Prepare for the next "Refresh" by making sure your Messages, Camera, and Video use the MMC for memory and not the phone (found in the Settings for each app). Also when you're reinstalling apps in step 7, make sure you install them to the MMC as well, unless you *have* to use the phone's memory for some odd thing. That'll make it a 3 step process the next time you need to refresh. I'm going to have to assume that like Windows95 reinstalls, this'll will be bi or tri-annual event.
There you go. My phone is definitely working much faster now and has almost a meg more memory to play with. Right this second, I've got 2.8MB available whereas when I started this process my phone regularly hung around 2MB or less.