You need to use the generic key if the system came with Windows 8.0 and are installing with Windows 8.1 due to bad design by Microsoft. For a system which came with Windows 8.1 your BIOS SLP key is automatically input with Windows 8.1 media. The media provided should be bootable.
After a crash I need tot reinstall win 8.1. With my XPS 8500 there was no disk delivered. If I want to download pre-installed software from the support web-site from Dell, it seems there is nothing happening.  On my Dell there is also a sort of OEM product-key so I can't use any other install disk...  What can I do? Thanks for an answer.
Need to reinstall win 8.1 after a disk crash