I installed a lot of music files from CDs in iTunes on my Mac but had to move this collection to an external hard disk when my computer started to run out of space. I thought I had done everything correctly, but now nothing works. Can you help? Name and address supplied DQ: There is nothing wrong with moving music files from one hard disk to another. Many people do this when they run out of space. Unfortunately, doing so is not as straightforward as one would expect. Let us assume your Mac's hard disk is called 'Mac1' and your external hard disk is 'Mac2'. You must now navigate to your music folder at: Users/username/Music. (The 'username' will be whatever you entered when you first set up the machine.) In that folder, you will need to find two files: 'iTunes Music Library.xml' and 'iTunes Library'. Open the xml file with TextEdit and do a search and replace for all occurrences of Mac1. (All references to Mac1 must be changed to Mac2. If you have named one of these hard disks something common like 'Beatles' you will be in trouble. You must ensure the names of the disks are unique and unambiguous.) Once you have done that, drag the 'iTunes Library' file into the trash. Restart iTunes, go to 'Import' under the File menu and choose the xml file you just edited. It should now work. Warning: playing around with these files is not a good idea if you are unsure of what you are doing. In any case, make backup copies of both the files mentioned above. In case it all goes terribly wrong, just return the backup copies to where they once were. I wish to buy a new Windows Vista-based computer to replace my Windows XP machine. How will I know if my existing peripheral equipment (such as printer and scanner) and their software are compatible with Vista? Also, must I re-register these devices after installation on the new computer? William Lo, Quarry Bay DQ: My confidence that Microsoft can get this right is not high. I did a search at Microsoft. com for 'Vista compatibility' and up popped what I wanted, in regards to both hardware and software. Sadly, when I clicked on 'Hardware Compatibility' I got an error message that said only Internet Explorer 6 and above could view the page. I realise using a Mac and Safari search may not please Microsoft, but why would any sane organisation design a Web page that only contained a list of names and other information for a specific browser? How does the company know I am not a Mac user looking to move to Vista? (We all know the answer to that!) I suspect Microsoft still has some work to do on compatibility issues. It should not be necessary to re-register your software, but you must be careful before moving everything over. Check with each software company before doing anything. That will be a chore but you have little choice.