|ah - you have the same laptop model as me (Inspiron 1525)!!|
I have never had this problem occur to me before, but here are my idea's
1. When you said "might have a virus" did you have an antivirus installed before this occasion, and was it kept up to date
If so, can you perform a scan from within safe mode?
2. If you cannot scan from within safe mode, or there is no virus found at what point in the booting stage does the screen turn "White"? And does windows completely crash or does windows continue to boot in the background?
Hopefully this will help diagnose the issue anyway :P