Parallells virtual machine get full!!

In need of urgent help!!
Hi, I´ve had Parallells installed for some years on my Mac book pro for some years. Parallells has worked fine up til now. The MAC has got a 250Gb hdd and 8Gb RAM. The problem now is that parallells VM gets full and windows tells me there is no hard drive space left.
This seems to happen frequently no matter how much I erase on the virtual machine. There is a lot of space left on the MAC drive so I cant figure out what is happening. The Virtual machine hdd was 100Gb but I reconfigured it to 128 and still windows tells me there is only 364 MB left!
Can anyone tell what to do? yours fransmo