Dell DOES NOT support Vista or Windows 7 on this model (no drivers).   Windows 7 will work in this model and Windows will install many device drivers but be forewarned that you MAY run into problems with acquiring all the device drivers and specifically the old Analog Devices sound driver.  Ultimately you may have to do as many others with older systems that do not have sound drivers, install a separate sound card to get sound.

Also, you will have to do a complete install, you can't use a Windows 7 "upgrade" option when going from Windows XP to Windows 7.

Hello Fireberd,

Thank you for your information.  For the Analog Devices sound driver, I have the driver but on this moment, my computer runs with a PCI sound card, I find the sound better than the internal sound.

In resume, my computer is ok for Windows 7 ?  I think that I will buy the complete version of Windows 7 and not an upgrade.

Best regards.

I think you can install and run Windows 7 on your computer without facing any problem. Your system supports it and don't worry about the speed of your computer after installing it.*

Don't buy the complete version of Windows 7. If you're running XP, you are entitled to the upgrade version which will save you some money.  There is no difference between the complete and upgrade versions of Win 7 except the price. 

You will, however, need to do a "custom" installation of Win 7, which will give you a clean install. You can do this with the upgrade version.

This link might answer some of your questions: http://windows.microsoft.com/en-US/windows7/upgrading-to-windows-7-frequently-asked-questions