You can reduce your risks of getting malware by following some basic suggestions. Here are a few.
Keep all programs and OS updated.
Do not install Java unless you need it...that's Java...not Java Script...If you do need it, disable when not being used.
Use Firefox browser with the NoScript add-on to prevent driveby installs of malware and other types of malware while surfing.
All Adobe products are frequently attacked by malware. Replace Reader with another 3rd party pdf reader or use Firefox for pdf reading.
Keep Flash Updated. One security update was released yesterday for Flash.
Email....never click on a link or open an attachment unless you have confirmed from the sender or other means as to where the link takes you or what is in the attachment
Use a NON administrative account except when absolutely required otherwise.
Pay attention while installing software and choose custom install when offered and Uncheck offers of toolbars and other types of adware.
I suggest you check in the link below first and if they are offered as downloads from there to use those as they are adware free. You have to
assume that ALL free programs and Add-ons are bundled with adware these days. Ninite - Install or Update Multiple Apps at Once
Avoid using P2P to download pirated programs, music and videos....some of the worse malware exists in those files.
As far as security programs go, everyone has an opinion as to which ones are best. I will suggest only to get either the paid version of Super Antispyware
or MalwareBytes AntiMalware. There are free antivirus programs such as Avast that will automatically update and protect in real time.
Use a Linux Live CD or Flash drive when doing banking or other financial transactions online. Many small businesses and home computer users have a Linux distro installed either
as a dual boot or on a separate computer that is used exclusively for financial transactions and not networked.
I do not know of any malware that is presently being used to infect Linux OSes.
NOTE: your XP is the most vulnerable to malware supported Windows OS. Microsoft will end support for it in April.