I need help urgently.........

My current os is WinXp Home (SP2). Everytime when during the windows
start-up, it always appear the following message:

Windows - No Disk

X There is no disk in the drive. Please insert a disk into drive A:
Cancel Try Again Continue

Under the Taskbar, is shown my firewall "No firewall is turned on"

After I click on the continue box, the error message disappeared and
firewall auto ON back again.

Pls kind enoguh to email me your reply to skyvansg@yahoo.com.sg

greatly appreciated your kind assistance.