@Marcus76 You've installed wrong certificate - for TOSINV[TOSINV00]2.1 SLIC, you need TOSINV-6E3ACBE4.XRM-MS or TOSINV-8A294E81.XRM-MS. Also, SLIC 2.0 is applicable for NT 6.0 (Vista/Server 2008) activation, not XP.