You install Windows on one (main) drive only.
With 1.5GB of RAM, you should be OK (2GB would be better).
As for security programs...
Spybot is a tool of the past.
I don't recommend AVG anymore since ver. 8.0 It became a hog with number of other problems.
- Avira free antivirus: http://www.free-av.com/en/download/1/avira..._antivirus.html
- Avast! free antivirus: http://www.avast.com/eng/download-avast-home.html
- free Comodo Internet Security (firewall + AV): http://www.personalfirewall.comodo.com/
NOTE. During installation, Comodo will also allow you to install AV only, or firewall only, if you prefer to combine one Comodo product with some other product.
If you decide to install Avast, or Avira, make sure, Windows firewall is turned on
, or use Comodo firewall..
If you decide to install Comodo Internet Security, or just Comodo firewall, make sure, Windows firewall is turned off
.IMPORTANT! Make sure, you use only ONE antivirus, and ONE firewall.
- SUPERAntiSpyware Free Edition
- Malwarebytes' Anti-Malware
(trial version is fully functionable): http://www.malwarebytes.org/mbam.php