http://www.synopsys.com/Licensing/Installation/Documents/install072/hspice_install.pdf
hope this helps somewhat.
we deal more with electronics and coding than IT stuff
unless we get a good look at where you went we won't know where to look.
there are common things though, try to search for it in the windows bar, check program files where most common installs go, check the file system hasn't hidden any folders or files... the list goes on.
if you can find your install directory that'll be a good start
One thing I do is try to install a package again. Most will give you the choice to select a directory (and you've probably installed it in the default one) and you can use this to tell you where you installed it