Installation fails: ENOENT error

Hello. I’m very new at Ruby and RoR. From Win XP I try to install Rails

C:\Ruby19>gem install rails
ERROR: While executing gem … (Errno::ENOENT)
No such file or directory - C:/Documents and Settings

I could not find how to solve the problem in the documentation. maybe a
path definition problem? any help welcome, I can’t wait to fire up my
web site! thanx in advance