ppm install http://theoryx5.uwinnipeg.ca/ppms/Net-SSH2.ppd

That's the wrong command for perl 5.10. Instead try:

ppm install http://cpan.uwinnipeg.ca/PPMPackages/10xx/Net-SSH2.ppd

Cheers,
Rob

Update: Or, for all versions of Win32 perl from perl-5.6 thru to 5.12 (including x64 builds of 5.12) the following should now do the trick:

ppm install http://www.sisyphusion.tk/ppm/Net-SSH2.ppd