Windows 7 won't start in Bootcamp

Hello Everyone:

Situation: A few weeks ago I installed OEM Windows 7 Home Premium 32 bit through Bootcamp 4 on my iMac running OS X 10.7.5. I was able to successfull install MS Office and other software and run them in the windows environment.

Issue: Over the last few days, whenever I've tried to reboot into Windows after restart (pressing "opt" key), the OS goes directly into Mac. I don't get the screen giving the choice of Mac / Windows / Bootcamp which would be normally expected. I also installed Parallel 9 Desktop for Mac and that too is not showing up the virtual machine for Windows.

Question: Before I delete Windows and reinstall, I wanted to reach out to the community and ask if I should run some more diagnostics to figure out the issue? Would greatly appreciate your insights.