did you choose the auto option to use the whole disc or did it manually?
try to use the auto "use entire disc".
if this works i would install xp to half of the disc and leave the other half as unformatted/unpartitined space.
then install mint and use the auto option of "use free space"
if this works you could install mint again do a manual partition, delete all linux partitions and create your own /, /home and swap.
this could all be due to resizing of the windows partition, or some windows/manual combo error.
I currently have on my main box a vista partiton (half), four root partitons for mints, swap and a home partition as well as free space.
Now where was i going? Oh yes, crazy!