Hello,
I have recently returned to Linux after many years absence. I found the Ubuntu 11.04 installation (via Wubi) a real surprise - no more re-re-re-typing command-line instructions etc. Anyway no problems with the installation and everything works BUT...
I installed it on an empty 60GB partition under Windows 2000 expecting it to use the whole (or almost) 60GB but it has only "formatted" 15GB, which means that there is little space for heavyweight software (developer's software and documentation, Intel compiler, bioinformatics stuff...).(Since it coinhabits with Windows, data storeage is no problem).
Is there some way I can "expand" the 15GB to, say, 55GB or do I have to reinstall the system?
Thanks in advance.

I think that by default Wubi, uses upto 30 GB (you have to configure that during installation).
However since you reside in a Windows OS, then you might as well use /host directory (pointing to the Windows HDD) to install surplus applications.

It can be very easily done with www.sysresccd.org. Download the ISO and boot the CD then run `startx` then run `the parted GUI` to resize the Linux partition. You may want to backup everything first.

You could try using a liveCD such as Parted Magic to resize the partition to take up the entire disk. Remember that to resize/repartition a disk, the partition(s) must be unmounted, thus the reason for using the liveCD.

I've never lost any data by resizing using gparted, but, I also don't risk such loss. I always make a backup of the partition I intend to resize "just in case".

You have been warned. Good luck with the resizing.

PS: Please pardon our respective manners. Looks like we all missed the fact that this is your first post at LQ. So, Welcome to LQ.

First of all I would like to welcome our friend as well in LQ. I would also like to apologize if I am mistaken in my advice, but is it possible to resize a WUBI partition that is nothing more than a file residing in a hard drive? If so, I guess that I just became wiser on that and I would like to thank our ramram29 and bigrigdriver (please do not mistake me as being ironic, I have no intention of that, as I do consider that if this is possible it is good news for me as well)

I haven't used wubi, but a quick google found the Ubuntu wubi guide - here it suggests you can resize ok.
A couple of of techniques are given in the referenced thread - I'd just go with the second post (presuming you used ext[234]).

Thank you all, your answers are very helpful.