The search engine was unable to find freeware, shareware and firewalls.
So, here's a free diagnosis site: www.tuneup.de
Scroll down for English language equivalent downloads.
Free firewalls:
"Zone Alarm Free" & "Comodo"

tuneup just found a wy32.mydoom virus which likely creeped in through either Google or through my provider www.Arcor.de

My PC was running slow and I downloaded Tuneup/

It is fantastic, much faster and easy and fun to operate.:)

Tuneup advised me to up my processor and my RAM. I'm running the originl Pentium II and a 192 megaherz RAM which, for paradoxical reasons, was more than enough for its time. Now, that DSL technology allows even more data to pass thru old lines, you can´t get by without installing at least Pentium III coupled with at least 400 mz RAM. As if replacing a normal automobile with a Ferrari to travel on the freeway, now that the traffic jam has been cleared.
A self-diagnosis program should be inherent in all operating systems