Hard Drive Full?

I have built myself a PC which dual boots XP MCE and another operating system of which legality is debatable, and it works great on the mac side *oops* but on the XP side, which is on a completely seperate hard drive., it says the hard drive has 23mb free, when its a 160gb hard drive. I only have 3gb of data on there, and it says this in disk defrag. but everywhere else it says it full. I had to install Acronis OS Selector to do the dual booting, so could this be the cause of the problem?

thanks!