"I have my hard drive split in three partitions and want to delete one empty partition and enlarge the other two using disk management tool in xp pro."
So for arguments sake you have your hard drive split with "C" + "D" + "E". "E" has no data but you want to merge the blank space "E" with "C" + "D"
No you can not do this with disk management as you are trying to alter the size of "C", it will not let you do this. This drive holds the operating system and windows will not allow you to change it.
Do you want to merge it with "D", it will let you do that, so the "D" drive is larger. You would have to move the data off "D" before you merged ( "C" will do if it has the space) and then you would have to delete the partitions of "D" and "E" and then rebuild them as one. You could then transfer the data back to the new enlarged "D" drive.