SpywareNuker is widely considered to be bad news. It's actually adware.
You can read what Symantec says about it here:
http://sarc.com/avcenter/venc/data/a...warenuker.html
There are more reliable scanning options availabe in Intranet Journal's Spyware Guide:
http://www.intranetjournal.com/spywa....html#scansoft
As for prevention software, I don't have personal experience with any, but there is a short list here:
http://www.intranetjournal.com/spyware/preventsoft.html