Unable to allocate virtual machine memory!

Yesterday I installed Parallels. I put the two files in the shared folder and was able to run parallels in both of my user accounts. Today, I can run parallels in one user but in the other I get the following error messate

I rebooted and downloaded and installed (repair) a fresh copy, to no avail.
Any clues?

 

Reduce the amount of RAM allocated to the VM.

For reasons I don't understand the optimum is somewhere around 800. On my machine (MacPro w 5GB RAM) if I allocated the max of 1500 I get the "unable to allocate" message every time. Around 1300 I get it sometimes, 1000 or less never.
Benchmarking shows there is no benefit allocating 1300 or 700.

 

I am sorry if this sounds rather arrogant, but did you try cleaning up your hard disk?

 

I tried increasing and decreasing to no avail. Reinstalling Windows worked.

 

Computer is 3 days old. Nothing installed except Parallels.

 

Here is what I did.
I installed Parallels successfully in User 2.
I moved the files to the shared folder
I ran Parallels in User 1
The next day User 1 couldn't run Parallels
I reinstalled XP in User 1
I can't run it in User 2