Check and select Windows XP (Service Pack 3) .
According to community discussions on Reddit , the registration requires both a name and a serial key: REVENGE S2K Serial Number: 1F10-11F2-0F16-04A2-8EC7-81F4-B1C5-5727 bud redhead registration key
Use moving platforms, secret ropes, levers, and slippery surfaces to outsmart Feyatta, the green-furred alien abductor. Check and select Windows XP (Service Pack 3)
: Filled with lush greenery and prehistoric hazards. and slippery surfaces to outsmart Feyatta
Upon paying—usually around $15 to $20—the user would receive a (often a name/key pair) via email. Entering this key into the trial version would "unlock" the full game, patching the executable locally rather than requiring a separate download.