Why disk space is not released after deleting virtual disk

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http://askubuntu.com – I installed ubuntu via wubi with the size of 20Gbs. Then i decided to increase it to 65 Gbs using this guide. Then i decided to delete this virtual disk (65 Gbs) to increase to about 150Gbs. The only thing i didn't follow the guide is that i delete this virtual disk from ubuntu using rm command (The guide seems mentioned to delete it from windows in the last step) After removing this virtual disk, i see the free disk space remained the same (not increased 65 Gbs as expected). Anyone know how to fix this, so that i can have 65 Gbs free space back? Thank you very much (HowTos)