If the problem is with Temp folder, then move it to another place:
Create new temp folder, e.g. C:\TEMP (make sure that your account has modify rights here, which should be by default in most cases)
My Computer | Properties | Advanced System Settings | Environment Variables on Advanced tab | User variables (top one) -- edit both TEMP and TMP -- point to the new TEMP folder
If the problem is with Temp folder, then move it to another place:
That helped! Thx! Now Ruby seems to run fine.