How to run autotest(Zentest)

Hi,

When I start the "autotest" it gives me the following error...not sure what HOME path I have to set...all Ruby/Rails related components are in path!

---
C:\>autotest -rails
C:/Tools/InstantRails/ruby/lib/ruby/gems/1.8/gems/ZenTest-3.3.0/lib/autotest.rb:285:in `expand_path': couldn't find HOME environment -- expanding `~/.autotest' (ArgumentError)
---
Any clues? Thanks.
Hari