asshu

Hi ! i am am using windows XP2.My system configuration is
Hard disk 250
Ram 1 gb
Giga bite mother board
Anti virus-->quick heal
am using BSNL WLL internet service.
since morning My system is being restarted again again.So i inserted the OS XP cd and -->Repaired the present OS (which is inC drive) .The system laiunched all programs after installation ,but immediately it started showing the error with a blue screen as there is error . No program is functioning.Why? Why is it happeing.And i also wanted to say that my screen display the color in pale yellow from 15 days.Is it also problem of OS or Power fluctuation?

As it show the error i again installed OS in other drive(F) .As i installed a fresh copy of windows,it's Ok now with this fresh OS .Now i wanted to know why the OS in C drive is like that?
How can I completely remove that old OS ?
I wanted to intall the Vista in the place of that OLd OS and use the newly installed XP Os also ?Can i do it?
Now my screen color is OK .But why it 's shown in pale yellow still morning?Is it problem of low voltage of power supply?