go into disk mangement ,resize (reduce) your main drive , and create a partition at the end of your drive ,say 1gb or larger . resize will shrink your partition (with your xp on) you can select what size ,it wont allow you to shrink it too much .
Before W7 erases XP it creates a Windows.old folder for your programs and data. So you can if you want to restore back to XP. The error not enough space, could be that your XP install with programs and data is larger then 21GB free space. I would suggest you move your My Documents and any other large folders to a backup device. This should give you more space.
I receive the exact same error message, alto I am trying to install from within Vista (and from what I've read, you have to have Vista SP1 installed to do the upgrade). I have this. I have a dual boot system, with the OS's on separate drives. When I boot to Vista, only the C: drive is visible (the drive with XP is hidden, so I don't think this is a problem). I first tried burning W7 to a disc and booting from that. The error I received there directed me to restart Windows normally and install from within it. I tried this and received error code 0x80070490. I then created a small partition on C: thinking, as the error stated, some space for installation files was needed. With this partition in place (labeled Z I tried again, only to receive the same error code. I am wanting to simply upgrade Vista; I don't like it and would be happy to use W7, even as a beta. I not dot want to do a full installation, as I want to keep my files. I'm not sure what to do at this point. Any expertise in this would be greatly appreciated.
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