Exaclty what is the issue aside from the lights? Is the system not turning on? Is it beeping? Need details.
This is the manual with the info you may be looking for
http/www.manualslib.com/manual/553492/Dell-Vostro-1088.html?page=60
If the light you are talking about is the hard drive one, if it's on solid for a long time, it is generaly a bad hard drive that causes that, it may be a virus as well which is making the drive run constantly. You can create a boot disk to test the drive, Hirens or Ultimate Boot CD both had drive test utilities in them. Create a disk, boot from it and run a disk check. If the drive is bad, replace it.