Not for the faint of heart...

..but this is the approach I would take to keep using WindowsXP and associated software *safely*: go with Linux.

I know, the Microsoft supporters are going to poopoo this - knee-jerk reflex - but here is what I've done:

-- upgraded RAM to the maximum the motherboard will allow
-- made sureWindows install disk and all Windows software's disks or downloads are at hand
-- backed up my data
-- either get a new drive (they're cheap enough these days) or - if your current drive is big enough or new enough - create a dual-boot setup with Linux Mint or whichever distro you decide to go with
-- install virtualBox with Additions
-- install WinXP and your software in VirtualBox

The benefit: as long as you don't get on the internet with the WinXP virtual machine, you're good. You can discriminatingly download (in Linux) and install OS updates (bug fixes) but as long as Windows doesn't get online, you're good. Use the Linux-version browsers such as Firefox or whatever: you can harden up Linux really well and will get the updates to the security fixes automatically if you go with - for example - Ubuntu or Mint, so you can dispense with AV and all the other rubbish you need running Windows natively with internet access. And you will enjoy Windows XP running as quickly as it did the very first day.

Caveat: if you run software that requires hardware acceleration, such as Windows-native video drivers to work, at this point VirtualBox is not a good solution.

Overall, this solution has allowed me to run MS Office 2000 brilliantly well as well as Photoshop CS3 (needed SP3 though...). It's the best of both worlds... happy