Daughter's computer is on the blink - may be a simple recovery or maybe worse, not sure yet. Anyway, one option was to connect the HDD as an external via usb as we have the leads and copy everything before we fry it in any repair. We can access the disc easy enough but she has a passworded account on her pc. So (her name) 'my documents' folder says it is not accessible. Obviously, in this mode there is no password entry option as there would be if she booted it up in her own machine. Any ideas before we stick it back in her PC and try booting from it again.

Assuming that you mean NTFS permissions are applied, then the administrator account of the host PC should have rights to any directories on the hosted disk.

At worst, the admin account should be able to "take ownership" and then grant itself RW access - this is only necessary where the admin group or account has explicitly been denied permission to access the directory or file.

However, if you mean that the directories are password protected by encryption, then you are screwed, as only the SID of the account that created the encryption can access them, and that SID would only exist in the installation on the original disk, when that installation is booted.

SD

Hmm - not sure - I think she just has a password protected logon on her own machine. Don't think any folders are password protected. But plugging it in as an ext usb drive on my laptop does not allow access to the 'hername's documents' folder. She's not here right now but I think next step is to try again with it in her pc. It might just need a boot from the XP cd and a repair.

This isn't an encryption problem. It's an ownership problem.

Have a look at this handy Microsoft technical document:
"Access is Denied" error message when you try to open a folder

Thanks - solved part of the problem by connecting the drive to my mac and that can read all folders so I've backed up all of her data. The problems with booting that she originally had revolve around, firstly, no or corrupt hal.dll file, then no or corrupt ntoskrnl.exe, then just unable to load windows. Done everything that is suggested in web searches and ms help pages to no avail. Next step is a windows re-install - hence wanting to back up the data.