problem with linux

hi everyone
i have recently installed ubuntu on my laptop using wubi installer,
ok now the problem is that when i boot up ubuntu it starts installation
after selecting the city and all when i click forward it says "starting disk partitioner" and then 1 message pops up saying that the partitioner crashed then i have three options
1.quit
2.continue anyway
3.try again
if i select try again then it starts loading and it never ends,
if i select continue anyway it stops installation
if i select quit it shows up the desktop it works but there is still instal icon on the desktop

ok now i tried to install through the desktop icon it works fine until it asks type of some disk partitioner it says like
1.Guided->use the entire disk
2.Manual
ya i have vista preinstalled in my laptop
well when i select manual it shows me all the partitions and when i try to select the 30GB partition (or even any other partition) it gives an error message, and of course the disk format is NTFS

please help me out i am really want to try ubuntu completely
sorry for such a long post
looking forward for the solution
thanks in advance

 

Do the Guided install, it won't erase Vista.