Partition size reduced during or after installation

I have 80 GB harddisk, partitioned into 4 drives of 20 GB each. I

installed XP on the first drive. However after intallation was done

and a couple of reboots, somehow the partitions changed. The first

drive (C:) reduced to 12 GB and an unallocated space 8 GB left between

C and D. Now disk Management Console has actions greyed out on this

space. Any idea whats going on and whats the remedy