To make an ISO "pre-activated," system files are often patched or deleted. This can lead to frequent Blue Screens of Death (BSOD), driver conflicts, and software errors that you wouldn't encounter with a clean, official installation.
If cost is an issue, consider:
The installation didn't look like Microsoft's sterile, blue-gradient screens. This version had been "personalized." The background was a low-res image of a neon wolf, and the progress text was written in a jagged, Comic Sans-adjacent font. The fans surged to a scream. The screen flickered a sickly green. windows+81+pre+activated+iso+64+bit+kickass+better+install