First, just out of interest have you tried running the diagnostic specified on this page:
Resolve Hardware Issues Using ePSA or PSA Diagnostics and Guide to Error Codes | Dell US
Personally I would at least try a clean install of some type. Now if what you say is true and Windows 7 is already on the system then it might be in a hidden partition so you can restore to factory defaults. See your support page on how this is achieved.
I think this page is for Latitiudes but do check:
Using the Dell Backup and Recovery Manager 1.3 | Dell US
Or you could try a clean install of Windows 10. You will need to download the iso and pop it onto a USB. This media creation tool will help you with that:
Windows 10
You should be able to use your Windows 7 key to activate or get the iso.
As a last resort you could always ask a friend with a machine that does have a DVD drive to help you turn the 8.1 iso from disk to USB
This guide shows how:
How to convert Windows 8/8.1 Installation disk to USB Installation drive
Resolve Hardware Issues Using ePSA or PSA Diagnostics and Guide to Error Codes | Dell US
Personally I would at least try a clean install of some type. Now if what you say is true and Windows 7 is already on the system then it might be in a hidden partition so you can restore to factory defaults. See your support page on how this is achieved.
I think this page is for Latitiudes but do check:
Using the Dell Backup and Recovery Manager 1.3 | Dell US
Or you could try a clean install of Windows 10. You will need to download the iso and pop it onto a USB. This media creation tool will help you with that:
Windows 10
You should be able to use your Windows 7 key to activate or get the iso.
As a last resort you could always ask a friend with a machine that does have a DVD drive to help you turn the 8.1 iso from disk to USB
This guide shows how:
How to convert Windows 8/8.1 Installation disk to USB Installation drive