Vostro 3450 -install Windows 7

Hello, it has a Window 7 sticker with legible license key. Can I download the install on another computer to a USB key and install from there? If yes, where can I download it from? 

You'll first need a license key for Windows 7 -- if you don't have one, there's no longer any way to legitimately obtain one (Microsoft abandoned Windows 7 in January, 2020 -- no security updates after that).

If you do have a license key, note that because it's end of life, it's not wise to use it online.  And we don't know how much longer you'll be able to run browsers, etc. on it -- once XP went end of life, websites began implementing security protocols to block it.  The same will eventually happen with Windows 7.

If you still want to install it, and have a license for it, just boot up your install media and away you go.

Welcome to the Dell Community @dCTAZ37 

https://www.heidoc.net/joomla/

Click on " Microsoft Windows and Office ISO Download Tool "

Then run.  " Windows-ISO-Downloader.exe "

I could not find an ISO for your exact model.

Under Dell ISO's the closest was a Vostro 3460 W7 (SP1 64Bit)

But you can still try the W7 download.

Best regards and good luck,

U2

@dCTAZ37 

Download and install Windows 10.  Use Windows 7 key to activate Windows 10. I did this on Monday.

I have done this for numerous laptops Lenovo, HP, Dell that came with Windows 7 and have had no problems.