You don't need to risk your PC's safety to create professional vector art. Several powerful, legal, and free alternatives work excellently on Windows 8:

If you specifically need for legacy file compatibility, consider using a virtual machine with an old licensed copy (if you own a valid license key).

Downloading a "portable" version of Adobe Illustrator CS5 from unofficial sources is not recommended

Inkscape is widely considered the best free, open-source alternative to Illustrator.