如何解决系统重装问题？

每次都要记得手动备份C:\Documents and Settings\Administrator\Application Data\Mozilla 比较不保险。
可以将Mozilla文件夹改在其他地方吗？

参考这个

Run Firefox from removable media
This advanced tip makes it possible to run Firefox from removable media, such as a USB memory stick. This will allow you to run Firefox with your personal settings from any computer, even those that don't have Firefox installed. It has only been tested on Windows XP/2000. The basic instructions are as follows:

Copy the Firefox application folder and your profile folder to the removable medium. In this example we will use R:\Firefox for the application folder and R:\FFProfile as the profile folder, assuming the drive letter for the removable media is R:.
Create a simple batch file called R:\Firefox.bat with the following line:
start \Firefox\firefox.exe -profile \FFProfile
Optionally, disable the disk cache to reduce the amounts of file writes to the removable storage by entering about:config in the address field of Firefox and set browser.cache.disk.enable to false.
The reason why a batch file is needed instead of a simple shortcut is that a shortcut uses absolute paths, and since the actual drive letter for the removable media may change depending on which computer it is plugged into, the relative path used in the batch file is guaranteed to work anywhere.

推荐 MozBackup，简单方便。

http://www.firefox-china.org/tools/mozbackup/

nighttalker：可以，建立新的用户文件，选择目标地址。
运行 "...\firefox.exe -p" 会打开用户文件管理器回到原帖

ok!

只要你可以确定你能从你D盘的用户文件启动FX,你就可以删除C盘的东西。
要确定这一点，地址栏输入： about:cache 看看你的disk cache到底在C还是D

我的Firefox安装在D盘，我建立了一个新的用户文件并放在Firefox在D盘的安装目录下。请问是否C:\Documents and Settings\Administrator\Application Data\Mozilla文件夹可以删除。

可以，建立新的用户文件，选择目标地址。
运行 "...\firefox.exe -p" 会打开用户文件管理器