Starting up XP takes ages, even after fresh install

Hi,

As off late, my PC takes ages to start. At the end it took even more than 70
minutes to start. This Monday I decided to install XP again. Yesterday I was
able to get the driver for my Ethernet card. After installing SP3 and a
reboot I installed the other necessary updates. I also installed my firewall
ZoneAlarm. But after the required reboot my system started to show the same
bad habits it had before the re-installation.

Some questions:
1. It should be impossible for a virus or spyware to get on my system during
installation (yes/no)?
2. XP works fine with the ZoneAlarm firewall (yes/no)?
3. Windows updates are tested and are not the cause of my system taking ages
to boot (yes/no)?
4. Is it possible for faulty hardware (broken DVD burner?) to cause my
system to take ages to boot (yes/no)? (Please elaborate)

And finally:
Do you have a suggestion for me what I should do? Install XP again?

Your help would be appreciated.
Abel