Yes you can, but be aware of this:
If the Windows 7 is installed on an NTFS partition (the default), your Windows XP must also be installed on an NTFS partition (not FAT32). Otherwise Windows XP will be unable to "see" any data on the Windows 7 drive.
Additionally, if some of the data you want to rescue is in any of the user account folders (eg My Documents, My Pictures etc.) you will need to "take ownership" of those folders to get access to them. See this for taking ownership in XP: http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/acl_take_ownership.mspx?mfr=true