MSMobiles has an article explaining how to do it. They claim:
easy to do
doesn´t break your guarantee
very useful to do because then you gain access to freeware and shareware (uncertified) applications - some of which are totally cool!
Of course there's a disclaimer: "(this)... article is based on instructions how to de-certify your SPV phone from CoolSmartPhone.com and on posts by people in the microsoft.public.smartphone newsgroup. Purpose of this article is not to copy the information provided there, but to present illustration of the unlocking process, with help of screenshots and photos, so that this process will be more easily comprehensible to users of Orange SPV cell phones."