another deployment problem

hi,
i'm using vb.NET 2003, CR XI and Excel 2003 as database. I'm connecting vb.net with excel using automation. And to connect Crystal reports and Excel, i'm using DAO. My project is working fine. Problem is in Deployment. mine is Windows XP. I deployed the project and try to install it in windows 98..installation is not happening. i tried in Windows XP & windows 2000 professional (both having office 2000)..installation done. but problem in running the project...it is not opening Excel (it gives the error "Object reference not set to an instance of an object")...can anyone help me on this?

if the details are not enough, pls let me know, i'll explain it..thanks..need the urgent solution