Helping people with computers... one answer at a time.
Reformatting a machine is a major operation that starts by erasing everything. Having a good backup is critical to preserving your data.
I plan to do a clean re-install of XP but am not sure of what absolutely must be backed up. Most of my important documents are on another drive but Firefox and Thunderbird in particular throw me. Where is my bookmarks folder and how do I back up my e-mail and address book? I assume that the program files folder should be backed up and I get the settings folder but I seem to have several.
This can get complicated, but it boils down to a very simple statement:
Backup everything, but expect to move only your data.
Oh, and it'll be a tad time consuming.
You haven't indicated why you're doing a reinstall, but you're definitely asking the right question to avoid data loss.
Let's start with the backup.
Prior to a reformat I backup everything. The entire hard drive. I might clear temporary files and browser caches and the like first to save some space, but ultimately I do not rely on myself to predict exactly what I should and shouldn't back up. I just grab it all. I dump it to CDs, DVDs, or even another machine on my local network.
These days it's actually a little easier since I use a true backup program it's already backing everything up nightly. (I heartily recommend you do something similar, regardless of whether you're reformatting your machine.) All I need do is simply make sure that I have the latest backup preserved before I begin.
The bottom line is that a day, a week, or a month or more later I can recover whatever it was I forgot from the image of my machine just before I reformatted it.
The data files for Thunderbird are easy to locate - backed up or not. In Thunderbird, go to Tools, Account Settings, and then click on Local Folders in the left hand pane. You should see "Message Storage" on the right which will indicate the location on disk where all the messages are kept.
Interestingly enough, I've had great success simply copying the contents of the grand-parent folder and getting not only all my messages moved, but extensions and other Thunderbird settings as well. For example, my Message Storage Local Directory might be:
However if I copy the entire folder tree from "...\Thunderbird", then I seem to get everything, including my mail.
I've not confirmed this as officially supported, but it works for me. Your mileage, as they say, might vary. Use with caution and of course, backup first.
The news is not so good for the rest of your programs.
While there are tools out there that claim to move entire applications from machine to machine, that's not what this is about. You're reformatting a single machine and looking to save and restore programs and settings.
Aside from the very occasional trick as I outlined for Thunderbird, I've not found a reliable way to do this.
The problem is that programs and their settings are scattered throughout your hard disk, Windows and within the Windows registry. It's extremely difficult to know exactly what needs moving.
The bottom line is that a reformat is more properly thought of as a "reformat and reinstall of everything". That means:
Reformat your hard disk (possibly as part of the Windows installation process)
Install Windows from it's original CD or other media
Install all your programs from their original CDs or other media
Re-customize all your programs
Reinstalling everything assumes, of course, that you have the CDs or whatever to reinstall from. In fact, this whole process is one of the big reasons you really want to take care to save every installation CD and every downloaded program. You'll need them again someday.
Re-customizing can be painful. After each re-install I find myself customizing less and less. Some programs make it easy-ish (Microsoft Word, for example, stores many of your customizations in its normal.dot template - restore that from your backup and many, though not all, of your settings are restored). Other programs don't, and you have to redo it all.
Having said all that, I know that there are utilities that are designed to move applications and settings from one machine to another or from one drive to another. I don't have any direct experience with these tools myself, so I can't recommend one. I also don't know if any of them will operate in this situation of saving and restoring applications and settings to the same machine and drive.
While many have reported success with application-moving applications, I tend to avoid them. Often the very reason for a reformat is to force everything to a clean initial state. It's unclear exactly what these utilities will move, and if I'm going to go through the pain of a reformat I prefer that my applications also be in that clean initial state as well.