First of all:

It is also the most commonly used one. The newly installed software is not that you can't recover the data, but that your operating program is wrong. Your new account (the date of establishment of the new account is the same as that of the old account) should be restored to 2008 first. When you want to restore the data of 2009, you must switch the year to 2008. At this point, if you want to restore the data in 2009, you must create a new database (.

Second:

Find the previous MSDE file (assuming that drive C was not installed before, the current MSDE is not under the same drive letter as the previous MSDE, and if it is under a drive letter, the old one will be overwritten by the new one), but the MSDE file inside will be overwritten by the new one after opening (the current machine name is required to be the same as the previous one).

Third:

Install the SQL database on your computer, and then restore the database. (Require that the previous MSDE file is not lost. )

Say so much first, leave a message if you don't understand. Your question is unclear. . . . . . . . . . . . Was there MSDE before? . . . .