I am using the latest ruby 1.9.1 windows installer.

gem env yields:

RubyGems Environment:
  - RUBYGEMS VERSION: 1.3.5
  - RUBY VERSION: 1.9.1 (2009-07-16 patchlevel 243) [i386-mingw32]
  - INSTALLATION DIRECTORY: c:/Ruby/lib/ruby/gems/1.9.1
  - RUBY EXECUTABLE: c:/Ruby/bin/ruby.exe
  - EXECUTABLE DIRECTORY: c:/Ruby/bin
  - RUBYGEMS PLATFORMS:
    - ruby
    - x86-mingw32
  - GEM PATHS:
     - c:/Ruby/lib/ruby/gems/1.9.1
     - C:/Users/Matt/.gem/ruby/1.9.1
  - GEM CONFIGURATION:
     - :update_sources => true
     - :verbose => true
     - :benchmark => false
     - :backtrace => false
     - :bulk_threshold => 1000
     - :sources => ["http://gems.rubyforge.org/", "http://
gemcutter.org"]
  - REMOTE SOURCES:
     - http://gems.rubyforge.org/
     - http://gemcutter.org

Any gem install fails,  but for example here is the attempt to install
rails:

Exception `NameError' at c:/Ruby/lib/ruby/site_ruby/1.9.1/rubygems/
command_manag
er.rb:161 - uninitialized constant Gem::Commands::InstallCommand
Exception `Gem::LoadError' at c:/Ruby/lib/ruby/site_ruby/1.9.1/
rubygems.rb:827 -
 Could not find RubyGem test-unit (>= 0)

Exception `Errno::EEXIST' at c:/Ruby/lib/ruby/1.9.1/fileutils.rb:243 -
File exis
ts - C:/Users/Matt/.gem/specs/gems.rubyforge.org%80
Exception `Errno::EEXIST' at c:/Ruby/lib/ruby/1.9.1/fileutils.rb:243 -
File exis
ts - C:/Users/Matt/.gem/specs/gemcutter.org%80
Exception `Errno::ENOENT' at c:/Ruby/lib/ruby/1.9.1/fileutils.rb:243 -
No such f
ile or directory - C:/Users/Matt/.gem/specs/gemcutter.org%80/quick/
Marshal.4.8
Exception `Errno::EEXIST' at c:/Ruby/lib/ruby/1.9.1/fileutils.rb:243 -
File exis
ts - C:
Exception `Errno::EEXIST' at c:/Ruby/lib/ruby/1.9.1/fileutils.rb:219 -
File exis
ts - C:
ERROR:  While executing gem ... (Errno::EEXIST)
    File exists - C:
        c:/Ruby/lib/ruby/1.9.1/fileutils.rb:243:in `mkdir'
        c:/Ruby/lib/ruby/1.9.1/fileutils.rb:243:in `fu_mkdir'
        c:/Ruby/lib/ruby/1.9.1/fileutils.rb:217:in `block (2 levels)
in mkdir_p'

        c:/Ruby/lib/ruby/1.9.1/fileutils.rb:215:in `reverse_each'
        c:/Ruby/lib/ruby/1.9.1/fileutils.rb:215:in `block in mkdir_p'
        c:/Ruby/lib/ruby/1.9.1/fileutils.rb:201:in `each'
        c:/Ruby/lib/ruby/1.9.1/fileutils.rb:201:in `mkdir_p'
        c:/Ruby/lib/ruby/site_ruby/1.9.1/rubygems/spec_fetcher.rb:
103:in `fetch_
spec'
        c:/Ruby/lib/ruby/site_ruby/1.9.1/rubygems/spec_fetcher.rb:
72:in `block i
n fetch'
        c:/Ruby/lib/ruby/site_ruby/1.9.1/rubygems/spec_fetcher.rb:
71:in `map'
        c:/Ruby/lib/ruby/site_ruby/1.9.1/rubygems/spec_fetcher.rb:
71:in `fetch'
        c:/Ruby/lib/ruby/site_ruby/1.9.1/rubygems/
dependency_installer.rb:99:in
`find_gems_with_sources'
        c:/Ruby/lib/ruby/site_ruby/1.9.1/rubygems/
dependency_installer.rb:192:in
 `find_spec_by_name_and_version'
        c:/Ruby/lib/ruby/site_ruby/1.9.1/rubygems/
dependency_installer.rb:213:in
 `install'
        c:/Ruby/lib/ruby/site_ruby/1.9.1/rubygems/commands/
install_command.rb:11
8:in `block in execute'
        c:/Ruby/lib/ruby/site_ruby/1.9.1/rubygems/commands/
install_command.rb:11
5:in `each'
        c:/Ruby/lib/ruby/site_ruby/1.9.1/rubygems/commands/
install_command.rb:11
5:in `execute'
        c:/Ruby/lib/ruby/site_ruby/1.9.1/rubygems/command.rb:257:in
`invoke'
        c:/Ruby/lib/ruby/site_ruby/1.9.1/rubygems/command_manager.rb:
132:in `pro
cess_args'
        c:/Ruby/lib/ruby/site_ruby/1.9.1/rubygems/command_manager.rb:
102:in `run
'
        c:/Ruby/lib/ruby/site_ruby/1.9.1/rubygems/gem_runner.rb:58:in
`run'
        c:/Ruby/bin/gem:21:in `<main>'

Thank you guys so much. I appreciate nay assistance you can provide me!