MS SQL BACKUP problem

[vhernz]

Hi,

I am new in MSSQL and recently encountered a problem in backing up the database. Here is the scenario

1. There is an schedule backup everyweek which overwrite the backup file everytime a backup is occured.
2. I need to update some script in sql. so what i did is to manually backup the database which also overwrite the old database file.
3. When SQL prompts that the backup is successful I thought it was totally all backup because i choosed the complete backup option.
4. Then I issue the sql script.
5. After this update script was applied, there is now a problem to the program.
6. So what i did is i delete the database.
7 Restore the database i backup
8. But the problem there are some data or transactions are missing. The only data that are left are those data until January 25, 2007 only which supposedlyuntil MArch 2 because i backup March 2.
9. When i check the properties of the database it says in the information that the last backup is January 25 instead of March 2.

Just want to ask why did this happen? which i am sure that i backup at March because the date of the file was change to March 2 instead of January 25.

I hope that this information is clear enough to help me
because i really need to put back the database until march 2

please help

thank you to all of you in advance!