When setting up your computer you really should have 2 accounts.
- An Administrator account ( Windows 7 ,Vista & XP , Apple)
- A Limited User Account ( XP ) Standard User (Windows 7 , Vista , Apple)
Then for your day to day activities you should run in limited / standard user which will avoid you installing or running unwanted programs and applications that you
Malware and Spyware require you to run in Administration mode as they need to access system files hence running in Limited will enable you to avoid activating these programs.
In Windows 7 & Vista the UAC is turned on and should be left on so that unauthorised changes to your computer are monitored.
if you have the 2 accounts you can also check if you experience software issues by swapping form one account to the other.