i've never tried xandros but since alot of distros come with GUI partitioners, how did you do it?, through the install? can you remember what changes you made to the hardisk?
When you start up the computer what happens? does it go straight into the xandros login?
You can try logging in as root with
Then enter your root password and type
This should give you a list of the partitions on your drive now.
If you deleted your windows partition well... i think you're stuffed and you'll need to re-install windows.