My Local Disk C crash after I install and use Comodo Time Machine. The first time I thought it was a virus and I reinstal Windows XP SP3. After I reinstall XP, I install again Comodo Time Machine and again the Local Disk C crash and don’t work well again. I set Comodo Time Machine to backup and protect only the Local Disk C, and then, only the Local Disk C crash. Local Disk C no longer work properly because the Local Disk C do not save any changes I made ( ex. I downloaded movie, muzic and save them to my Desktop, then wen I dit a system restart, all the moves and muzic gone and I ghet error mesajes ) after I restart the computer. So this time, is not a virus. I dezintall Comodo Time Machine and everiting come back to normal. Comodo Time Machine is a danger program. I’am scare to use it again. Maibe is not compatible with Avast 5. Please repair this problem Comodo 
Do you have enough free space in drive C ?
regards
Haibo
Yes I have a lot of space. I have 94 GB free space in Local Disk C, and 121 GB free space in Local Disk D. The space is not a problem.
I have Avast 5 on Vista laptop (two partitions on one drive) and CTM works flawlessly, although I know you are having trouble on XP machine. I also have it on XP desktop but anti-virus is a-squared on that machine.