I just installed Arch Linux and it's not working well, and now I can't access Windows because of GRUB. How can I uninstall GRUB through the Arch Linux shell?
You cannot 'uninstall' grub. You can overwrite it by Windows bootloader. I'm afraid that most people who know how to reinstall Windows bootloader without reinstalling Windows are on superuser (I guess for most people here Windows is the second system) - you have to do it from Windows install disk or similar tools.
You should be able to chainload the Windows bootloader from grub by following code BTW:
or entering commandline in GRUB
PS. What is not working well? It is part we can help with. Have you tried simpler distributions like for example Ubuntu?
I had to get rid of the dual boot in my work computer (needed space for work stuff) and I used the MBRFix utility which you can download here: