how to install a new windows 7 on my laptop with the serial number under the battery

Yes it will, but if you use other than the Dell OEM media, you will need to call Microsoft to activate after installing.

www.dell.com/.../ArticleView

do u know where i can download a dell oem media because the windows i have is a bootable one from microsoft sp1

or can it work ?

Assuming you have an installation at the factory settings and you want a clean installation. Follow my Windows Reinstallation Guide/A Clean Install of Windows 7:

http://philipyip.wordpress.com/dell-community-forums/

If you follow step 1c of this wiki and backup the product activation files using the Activation Backup Recovery (ABR) program then you may download the Windows 7 Home Premium 64 Bit with Service Pack 1 .iso from Digital River to clean install Windows 7. The combination of the Digital River .iso and the ABR program effectively give you a Windows 7 Reinstallation DVD. After installation, you can then restore the product activation files (Step 11 b). This product activation mechanism uses a system locked preinstallation key i.e. a generic key assigned to all Dell systems running Windows 7 Home Premium - this SLP OEM activation will only work for eligible systems i.e. Dell systems which came with a Windows 7 Home Premium COA. I am trying to make a backup of these SLP keys activation files for all variants of Vista and 7 and you can see the notes on WordPress about the files I need to do this alongside instructions/notes - you can help me with it if you want.

Also just to note you have the 25 digit product key and can also input it with the Digital River .iso and activate by phone (Step 11e) but it is far easier to use the Activation Backup and Recovery Program opposed to activation via phone. However phone activation gives you a second method to activate just in case.

The guide also explains where to get the drivers and other preinstalled software. This system is not a Media Direct System so Step 7a and 14a don't apply.