who else is still on XP - and I mean a LOT of XP

We have around 100 XP machines. Only have three Win 7 machines and those are either IT machines or a conference room machine. We've been close to moving on Win 7 for a couple years, but business needs leave us only certain windows of opportunity to do it. Another issue is an IT staff of two and both positions have had turnover which upends planning. I'm hoping to finally get images and a plan in place by the end of tax season. As an accounting firm, nothing can be done between Jan and mid April, except planning.