I used the registry cleaner (latest version) for the first time today and it made XP Home (SP3)'s defragmentation tool inaccessible. Only after I restored the backed up registry did the defragger become available again. After cleaning the registry, I selected my drive, selcted properties, went to the tools tab and the option to defrag was grayed out and said no defragmenting tool was installed. Until this bug is fixed, I won’t be using this application anymore.
I used the registry cleaner (latest version) for the first time today and it made XP Home (SP3)'s defragmentation tool inaccessible. Only after I restored the backed up registry did the defragger become available again. After cleaning the registry, I selected my drive, selcted properties, went to the tools tab and the option to defrag was grayed out and said no defragmenting tool was installed. Until this bug is fixed, I won't be using this application anymore.
Sorry for your trouble. I suppose you used the Comodo Registry Cleaner that is distributed on http://registry-cleaner.comodo.com/index.html , not the Registry Cleaner included with Comodo System Cleaner RC?
LA
Ps1. I made a topic split since I think your post deserves its own topic. (:m*)
Ps2. Welcome to the forum. 
Hey man, that happened to me too.
It occurred while using the stand alone comodo registry cleaner.
There is a registry key the ends with a reference to “defragpath”. Mine read
“HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Explorer\MyComputer\DefragPath”
And you should uncheck that reference and place it in the “ignore” list. Easy to do, really.
And here is what I did to put defrag back on my machine. I use XP home SP3, don’t know what you use.
In your C:\WINDOWS folder there is a folder called “INF”, it is a hidden folder so you have to turn on the “show hidden files and folders” in the Control Panel, Folder Options, View tab, just a little way’s down the list of options.
In this inf folder look for a file called “dfrg”, (not the “dfrg.pnf”, which is right below). Ok, on the “dfrg”, I right clicked it, chose install, and that solved my problem. Takes it 2 seconds to do it. No probs.
Regarding the nature of this problem, I suspect it has to do with using other third party defraggers in the past and in the install/uninstall something somewhere get’s messed up. So the registry cleaner thinks it’s a useless entry and you know what happens then. That is just my opinion.
But, don’t be afraid of the comodo reg cleaner. Just run the scan again and look for the defragpath reference, just uncheck it and then choose the ignore feature for it too.
Thanks for the input!! I solved my problem with the “disappearing defrag tool” by restoring my registry using ERUNT. I had another problem caused by the stand along registry cleaner - my DVD drive was made inaccessible and in the device manager, there was a yellow triangle next to its name. Its icon did not shopw up in My Computer either. Fortunately, I made an ERUNT backup and the restoration solved both problems.
Thanks for the helpful tip, though. I will be staying away from this app. Who knows what else got corrupted.