Ruby suddenly stoped working

I am new to ruby. Installed v 1.8.6 with rubygems 1.0.9 yesterday, 9
May. Everything was working last night but stopped today when i booted
my laptop. Running vista ultimate.

The ‘ruby’ command is not recognised.
I’ve checked the environmental variable and is set: c:\ruby\bin. Also
RUBYOPT="-rubygems" is also set. Please help. Thank you.