Source :Virtual PC Windows 7

Event 148, Virtual PC :
The volume 'C:\' only has 18 MB of space left.The virtual hard disk 'C:\Users\saravana\AppData\Local\Microsoft\Windows Virtual PC\Virtual Machines\Windows XP mode.vhd' associated with the virtual machine 'Windows XP mode' has been expanded, and very little space remains.The virtual machine will be paused.
source : virtual pc
event id : 148
log name : Microsoft-Windows-Virtual PC
Product name : Virtual PC host process.

Event 167, Virtual PC :
The virtual machine 'Windows XP mode' could not be started because there is not enough free space remaining to hibernate state on C:\.There is only 133 MB available. Virtual PC needs approximately 288 MB to hibernate this virtual machine.

Event 1000, Source : Virtual PC : 
Virtual machine 'windows xp mode'.Error - The virtual machine could not be started. There is not enough disk space available. (0x80070070)


Solution : Free the disk space by deleting unwanted files and use disk cleanup tool.Now, starts running the virtual PC,the problem is solved.