I have installed Windows XP SP3 with all default options and created a guest account(without any password). I was wondering, if this is enough to prevent any user from corrupting the main Windows account(such as introduce a virus), while being logged into the guest account. Assuming these users don't know about BIOS Startup and will just log in as Guest, now much harm can such account inflict on the main account.
Can a Guest Windows XP account infect the overall system with Virus?
Yes. This is possible through various security exploits. Windows Updates help close design flaws that exploits exploit. So run that frequently and that'll help prevent this kind of abuse.
Under regular use, a guest account should be fairly incapable of ruining the system. However, if they have physical access to the machine, then they can easily boot off another device (usb, for ex).. Then use easily available utilities to crack your admin password and do other entertaining things you'd rather prevent.
-- Ammendment --
I'll add that a under-skilled user can do this inadvertently. So the integrity of the content they consume matters. If they're going to really sketchy websites, they could unknowningly run an exploit that owns the system and uses it for whatever (like a spam botnet).
I know that the answer is yes, from a guest account it's possible to affect the main windows account (let's say, the admin one).
But I was searching for specific examples of it and couldn't find any, just general ones: