I don't like the Disk Management console in XP or Vista. It has limited features and often refuses to shrink a partition as much as you wish, for no apparent reason.
It's better to use a non-Microsoft partition manager. The best free one is gparted which you run from a bootable CD.
GParted -- Download
GParted -- Documentation
The best buyable ones are Paragon Partition Manager or Acronis Disk Director (not Partition Magic which is not compatible with Vista). They have wizards to make some jobs a bit easier than in gparted.
In gparted, you would do the job in steps like this:
Note: "Free space" is inside a partition and can be used for saving files into. "Unallocated space" is outside of any partitions and is useless. If you delete a partition, that area of the disk becomes unallocated space. It's only useful for saving files into after it has been added to the inside of another partition.
Note 2: In gparted you can only add or remove space at the end of a partition, not at its start.
To end up with one big partition:
Delete the Linux partition.
If the Linux partition was at the start of the disk (left end of the diagram) you will now need to Move the Vista partition to the start of the disk.
Now you can resize the Vista partition larger, so it includes all the unallocated space created by deleting Linux.
To end up with two NTFS partitions:
Delete the Linux partition.
Move the Vista partition to the start of the disk if it wasn't there already.
Maybe resize the Vista partition smaller or larger, to leave enough unallocated space for the new partition.
Make a new primary partition using all that space. It should be NTFS type if it's for a Windows OS or for data files which Windows can read and write.
Vista doesn't mind having its partition resized by another program such as gparted. That only changes the end position of the Vista partition.
Vista does NOT like having its start position changed, which is what happens if you Move it in gparted. That will probably stop Vista booting. You can fix it easily though:
After quitting gparted, if Vista won't boot from the hard disk, boot the Vista DVD. Go through the Language settings page. On the next screen, click "Repair...". It will offer to repair Vista's startup.
One more note:
In gparted the limit of how much it will allow you to shrink a partition should be how much free space is inside it, because it doesn't want to destroy any files, only steal unused space.
However the limit of what you can remove is actually the distance from the last file to the end of the partition. So it helps if you defrag the partition before running gparted, so the files are all near the start and the free space is all at the end.
Some partitioning programs such as Paragon and Acronis include a defragging feature.