You do not need a registry cleaner if you are going from XP to WIndows 7 since installing WIndows 7 on an XP machine does not retain any operational part of the registry or of XP itself. Here's the content of a message I posted this morning in the Norton Forums and now just in the other Windows support forum here dealing with going from XP to WIN 7:
With XP any way you do it is a clean install! You can't upgrade XP and preserve the applications etc, which on the whole is a good thing.
But you can do three kinds of "Clean install" with XP and Windows 7 if you retain the drive that Windows is on:
You can dual boot by starting the installation from within XP -- that preserves your old XP and adds WIN 7 in a new partition or on a different drive, logical or physical.
You can do a clean install in which you wipe the hard drive or only use the new drives and start from scratch in which case you do boot to the DVD
You can do a clean install from within XP which saves part of your XP files into a folder WIndows.old and then makes a clean installation of WIN 7 in a clean area of the disk ending up with WIN & installed clean but a bunch of files in a folder within and accessible directly from Windows 7.
In addition you can use the Windows Transfer Utility with any of those to save certain files and settings into an off system location and then move them back later before you install the associated applications so that when you do install the applications (and you do this after using the transfer utility to bring them into WIN 7) they find your files and personal settings waiting. It does seem to move cookies and desktop icons but may depend on the settings in the associated settings of the transfer utility. Again there's a degree of uncertainty about this.
Each of those has its pros and cons. The only downside of the third route is a degree of uncertainty at present on what files are saved into that Windows.old. It may not be all you want in terms of personal data files and might, for example, only be those in certain default locations. This applies to the Transfer Utility too.
Needless to say it would be more than a good idea to make an image of your XP drive and store it off-system in case you should need it and absolutely essential to make backups of your personal files like email and images etc that only you can identify since, for me at this moment, there is more than some uncertainty as to whether the files moved into Windows.Old or transfered by the WIndows Transfer Utility automatically include say for example all Microsoft Word document files wherever you have stored them on the drive or only those stored in the default locations .... or ....
The support available on the Microsoft Windows 7 Help pages is extremely detailed and helpful. Do please go there, read and download the Instructions for going from XP to WIN 7 -- on the specific XP page there is a link to the instructions in PDF format; I clicked on that and when it asked Open or Save I saved to my computer so I could read there at leisure when ever I want and use the active links in them for more but I also printed them out. There are 12 pages for XP to WIN 7 but I printed mine doublesided and they are the best 6 sheets of paper I ever printed out!
Windows 7 Help
Install, Upgrade and Activate
Specific XP to Windows 7 instructions
There's even a video on the last one although I've not watched it yet.
I hope that helps -- going back to the beginning. I don't know of a Registry Cleaner that is not capable of doing more harm than good!
Hugh | 
