Problematic dual boot

[Lisi Reisz]

Good evening all!
Sorry - the bad penny has turned up again.... ;-)

The dual boot is XP/Kubuntu Hardy Heron.  One runs perfectly, the other has a 
very persistent virus that can, surprise, surprise, disable virus scanners.  
I don't need to tell you which is which.

The owner has given me complete carte blanche.  "Do whatever you think needs 
doing."  A bit nerve-wracking. ;-)

As I said, his Kubuntu is running beautifully and has been thro' several 
upgrades and a year or two.

XP has been left alone to sulk.  But now there is a must-have 
Windows-or-Mac-only application.

I have tried to repair XP.  I have tried to rid it of viruses.  But no luck so 
far, and I am running out of time.  (I have a deadline.)  So I need to start 
looking at other options.

His system is:  AMD Athlon 64 3500+; FoxconnK8m89OM2MB-RS2H motherboard; 1 
stick of 512MB RAM.  

I am looking at reinstalling XP, while trying to leave Kubuntu alone, which 
could mess up the MBR; or telling him that he needs more RAM and using 
Virtual Box.  

As a long term solution the second seems to me to be the better, but it would 
mean missing his deadline and returning the box and having it back again 
and - and more seriously - I have never actually installed VB, and cannot do 
what I would normally do in this situation and install it on my own box first 
because my box is not up to it.  

What would you lot advise?  Or what would you do in my shoes?  If installing 
XP with the Kubuntu partition as it is now would indeed, as I suspect, muck 
up the MBR so that Kubuntu became inaccessible, how easy would that be to 
fix?  And how would I fix it?  And am I right in thinking that, with more 
memory his system would be powerful enough for VB.  The maximum RAM his board 
can handle is apparently 2 GB.

As a last resort I have permission to reinstall the lot if I deem it 
necessary, but am reluctant to do so when Kubuntu is running so well and when 
he will inevitably have tweaked it in many small ways over time.

TIA
Lisi