Wierd folder in C drive

G_M

C:\1b4cfeb6948d4ae730cf3f3a

Inside are more folders with titles like ar cs da DotNetClientFx

Anyone any idea what these are?

S0litaire

It's a temp folder created by a ".NET" when you install it.
it can be removed if you like. (although the install program should delete that folder after it finishes!)

John_Gray

Wot he sez.
If it won't delete, then you might need something like Unlocker. (If your AV or browser objects to this site, try FileHippo or Softpedia.)

JasX

as above, microsoft can be a bit sloppy leaving 'backup' copies associated with larger patches/service packs.

you shouldn't need to install any additional software if you manually give yourself / the administrators permission to 'own' the files (google it) as you'll then be able to delete them. however a software route might prove easier depending on how technical you are...