Assuming this is an Inspiron laptop rather than desktop, the key would've been on a sticker located on the underside of your system or perhaps inside the battery compartment if the system has a removable battery.  If it's an Inspiron desktop, it should be on the back or top of the chassis.  If you don't see it anywhere, then the only way to get a replacement key would be to buy one; nobody issues free replacements.  However, I'm not sure Windows 7 keys are even sold retail anymore, and you would not be able to purchase a Windows 10 license and downgrade to Windows 7.  Although Win10 accepts Win7 keys, the reverse is not true, and I think from a licensing standpoint, downgrade rights are not included with retail licenses anyway.

Ok, I think I have located the activation key as had writing it down and kept somewhere.. does it mean I can reinstall windows  in new HDD. Also wouldn't that key be locked to  os recovery  provided by dell only?

Ok.., great, thanks for the help.

If the key is correct, then yes you can reinstall Windows 7.  The key would NOT be locked to Dell's media only.  You can download a Windows 7 ISO directly from Microsoft, then just make sure you install the correct edition for your system's license (Home Premium, Pro, Ultimate, etc.).  Worst case, automatic online activation may fail due to the hardware change (and I've seen some OEM keys not activate before), but in those cases you can just use the automated phone activation system and you should be fine at that point.

Hi there, received the new HDD today, just wondering which version window is for my computer.

When I  run Windows iso downloader  it gives me option of either

Windows 7 home premium sp1

                  Or

Windows 7 home premium sp1 COEM ( under  OEM)

Iam not sure as only thing I know that my machine came with windows 7 home premium 64 bit..

Any help ?

Hiya, thanks for the reply. It's Inspiron n5010.

Tried to install windows does ,but windows cannot be installed on this disk. The selected disk is of the GPT partition style.

I understand coz it's been formatted and partitioned on other computer and need to convert to MBR.

but for some reason shift+F10 won't open command prompt window for me to use diskpart.

Any suggestions?

Forgot to mention I can delete the partitions, but have copied some 100gb data which I want to keep.

Wow it works , WINDOWS ACTIVATED,.. you are the best Philip Yip , .. I have been on many forums and either no-one has enough knowledge or they simply don't care.. thanks alot

Wow it works , WINDOWS ACTIVATED,.. you are the best Philip Yip , .. I have been on many forums and either no-one has enough knowledge or they simply don't care.. thanks alot

Great thanks for letting us know. If you want your Free Upgrade to Windows 10 then use the GenuineTicket.xml method:

http://dellwindowsreinstallationguide.com/the-initial-clean-install-of-windows-10-using-a-faded-windows-7-oem-coa/