Can you backup programs to reuse on a Windows 'downgrade'?

I purchased a copy of Windows 7 Ultimate on Amazon about 6 months ago through a 3rd party and it was recently declared 'not genuine' by Microsoft. I had my 'bargain rate' payment refunded by Amazon (the seller sent me Ultimate by mistake - I ordered Premium - and told me to keep it).
I've been using it on a laptop and already have Windows 7 Pro on my desktop so I've decided to uninstall it and reinstall XP.
My questions is can I use a backup program - I'm thinking of Comodo - to backup my software and programmes and reinstall them after I've 'downgraded' to XP to avoid the lengthy process of installing them all again?