This a common question and my stock answer is this:Microsoft Antivirus Adobe Java
Anything else consider carefully. For instance, if you have a HP printer and you get offered an update by HP then by all means have it – but its probably not essential. Read the window carefully and un-tick any other things you may be asked to download – otherwise you’ll end up with toolbars and scanners you don’t actually want.Explanation: Microsoft – Windows is continuously improved – you might as well get the benefit Antivirus – new viruses are uncovered daily – your antivirus product needs this information. Adobe – so much animation and ability to view moving images on the web is dependent on the Adobe products. So too is the ability to view PDF files, so accept Adobe updates. Java – many web pages depend on Java to help you fill in forms, animate the cursor and do other minor jobs in the background. You need Java.