This is a common problem that surfaces when you install a Windows OS after you install Ubuntu; Windows conveniently wipes out the GRUB bootloader (the Linux equivalent of NTLDR, the “Choose Operating System menu”), locking you out from booting into Ubuntu. The fix for this is quick and easy in the typical case:
Crawl The Blog
MeI'm a computer science undergraduate at BITS - Pilani Goa Campus.
On My Mind(Still) Being enlightened by Hal Abelson's, Jerry Sussman's and Julie Sussman's Structure and Interpretation of Computer Programs (MIT Press, 1984; ISBN 0-262-01077-1); with Clojure!
In Utero: Alpha Testing