It's quite easy to do so. You just require fdisk and ntfsresize (Check your software repositories to have both installed. fdisk usually is).

With fdisk -l /dev/sda you can make a backup of start/end points of your actual setup. As long as you don't format the partitions - all is safe. Example output would be

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1        2550    20482843+   7  HPFS/NTFS
/dev/sda2            2551        7415    39078112+  af  Unknown
/dev/sda3            7416       10000    20764012+  83  Linux
/dev/sda4           10001       24321   115033432+   5  Extended
/dev/sda5           10001       10262     2104452   82  Linux swap / Solaris
/dev/sda6           10263       13041    22322286   83  Linux
/dev/sda7           13042       19121    48837568+  83  Linux
/dev/sda8           19122       24321    41768968+  83  Linux

In this case - delete partition 2 - and replace the end boundary of partition 1:

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1        2550      39078112+ 7  HPFS/NTFS

After that - just run ntfsresize with:

ntfsresize /dev/sda1

It will automatically adapt the ntfs journal and size informations to the new size and schedule a filesystem check for the next Windows XP Start.
Windows - after starting up - will want to restart as it has discovered new hardware (the bigger disk). After that restart - you're done.