Why dont you consider installing Ubuntu for a change ? I'm not sure if antivirus/firewall vendors are even supporting XP and you really dont want to be running XP without protection.

Perhaps you use a lot of Microsoft Word - Google Docs is a fine replacement. For basic Excel use, Openoffice/Google Docs is good enough (problem happens when you are doing advanced macros).

Perhaps you use Photoshop - Gimp is a fine replacement unless you are using it professionally.

Why dont you mention your specific OS software needs and we will be happy to suggest alternatives.

FYI, my entire family (wife, parents) use Linux and are pretty happy with it.