@Shaunak, I think you installed some Vista theme in Ubuntu!! Is that right??
Tell me what's your problem? I want to know how much space you have allocated
for root('/') & swap? Are you running short of space or getting some errors?
In case you want to install Themes in GNOME the easy way, install the package, gnome-art.
$ sudo apt-get install gnome-art
After installation launch the application. If you choose 'Application Icons' all the
Application icons themes(preview) from GNOME website would be downloaded!!
If you click on 'Install' the theme will be downloaded from the Net & installed.