Installed kali, regreted it, wanna go back, dont know how.

Hello, everyone. I recently, out of curiosity, installed kali. I must have done something wrong because i now cant go back on windows--even when the cd where i have kali is removed, i still cant go back on windows, it only appears <<no operating system detected>> or something along these lines. My pc is almost without any memory left therefore i cant download windows into a pen drive and reboot. Tbh i just wanna go back to windows, it clearly was a mistake walking into an unkown land. What can i do

Well, first use the Windows CD to repair the Windows install. Then Delete the partition created and extend the Windows partitions. Google has all the instructions to do both of those things (that are not specific to kali).

You might have switched to useless Legacy BIOS setting which is preventing Windows to boot. Switch to UEFI.