Well, it really depends. On one hand you have the phrase "better safe than
sorry" which is applicable in this situation. But it also depends on how
much you use the internet and what kinds of websites you visit.

In my opinion, a good security set up for a computer on a router (and I
assume broadband) should consist of A browser that doesn't use activeX
(Firefox or Netscape), a AntiVirus, a Firewall (Software, on the computer in
addition to the one on the router because the router does not filter
outbound connections), 2-3 AntiSpyware (1 paid and 2 Free I recommend
Ad-Aware and Microsoft AntiSpyware for the free. McAfee, Webroot Spy
Sweeper or Spyware Doctor for the Paid. Using only one of the paid will
work.) Yes Spyware Doctor will work and it will not take up any more space
than any other AntiSpyware. No AntiSpyware is a Magic Bullet so it is
important to use the combo I listed above or something like it. Personally
I use McAfee Internet Security suite and McAfee AntiSpyware along with
AdAware and Microsoft Antispyware and I use Netscape for my browser.

But again, it all depends on your needs. I need the internet for my job and
I can't afford any down time and I have to go on a number of sites where the
security of the site is not clear

Also, if you are have problems with SPAM run a spam filter. SpamKiller by
McAfee works well.