I have tried that and now get 'The file specified is not a virtual disk.
Okay, the type of virtual disk being used is a twoGbMaxExtentSparse which means its a split disk where each segment can grow to 2GB and these as binary files while the Disk DescriptorFile is a text file. The Disk DescriptorFile files "Windows XP Professional.vmdk" and "Windows XP Professional-000001.vmdk" appear to be okay, show no obvious signs of corruption and the information they contain appears to be proper. What I cannot tell you is the state of the binary segments, then ones ending in "*-s001.vmdk" ~ "*-s021.vmdk" and if any of these are corrupt then there is a problem, One that may or may not be able to be fixed and this is why one should always have up to date proper backups so when things like this happen it no big deal to recover from.
BTW I assume that you have a backup copy of this Virtual Machine as you have attempted to get it working and if you don't then you should, even if in the end it can be recovered you need to have a backup as to proceed forward.
In your PM you said you just need to get something off the disk and if this was VMware Fusion 3 you could just use VMDKMounter to attempt to mount the disk and retrieve any User Data however VMware has removed VMDKMounter from VMware Fusion 4! (I'd say something here about them removing it however it should really speak for itself how bad a move on their part it was!)
One can use VMDKMounter from VMware Fusion 3.1.3 and install it under VMware Fusion 4 using information in the following thread and read the entire thread before proceeding. Have a look at: Fusion 4: no VMDKMounter
This will enable you to (attempt to) mount the virtual hard disk "Windows XP Professional-000001.vmdk" manually by ctrl-click and select Open With > VMDKMounter and it mounts the virtual hard disk as a volume on the Mac. The if it's not corrupted you may be able to retrieve the User Data.
You could also remove everything from the Virtual Machine Package except for the .vmx file and all .vmdk files and then attempt to open it normally. If working with just the .vmx file and all .vmdk files doesn't enable the virtual machine to boot normally then your options are the VMDKMounter route or attempt to repair the virtual hard disk with vmware-vdiskmanager.
What are your thoughts? 