Shrink Windows partition to permit a UBUNTU partition

[elmo]

A friend wants to install UBUNTU 8.04 on his computer that already has 
Windows XP.

Defrag did open some space at the end of the current Windows partition 
but my estimation is that it may not be large enough for a decent sized 
UBUNTU partition.

Windows Defrag indicates that there are several spaces between data 
blocks in the C: partitiom so if there was a more effective defrag, 
there'd be plenty of space at the end of the C: partition for a UBUNTU 
installation.

Can GPARTED do a safe job of shrinking the C: partition and create a 
decent sized UBUNTU partition without loss of Windows:data?

Any hope ?