I am not able to view my Boot loader screen today after I installed Windows Xp Sp3 in another partition Earlier I could select either Windows Xp-sp2 Windows 7-32bit or Windows 7-64bit?

I had the exact same problem with my own computer. Apparently, Windows 7 doesn't work that well with Windows XP's boot loader (when dual booting). I solved the problem (well...sort of) by booting into my Windows 7 partition, Installing EasyBCD (http://neosmart.net/dl.php?id=1) and adding Windows XP to the boot loader again. The only thing is that when ever I boot into Xp (which is rare now) and then shut down, the Windows 7 boot loader is erased an I have to recover the computer with the Install DVD.
The Windows Boot Loader begin erased may or may not happen to you, but it may

Best of luck with it,

~Dex1010