Every new account created on a Windows XP PC is a full-blown Computer Administrator account. Some people think that you shouldn’t use Administrator accounts for everyday work, that most users only need a limited user account. Many Windows XP experts suggest that you create two accounts for each user:

The rationale is straightforward: If you’re using an Administrator account and you accidentally run into a virus (or a Trojan horse, worm, or the next big, scary security threat), that bad program automatically inherits your authority. So if you’re using an Administrator account, the bad program can wipe out your hard drive or do just about anything it likes. In actuality, though, the level of protection afforded by running as a limited user isn’t all that great. Malicious programs that can crack Outlook’s address book, for example, can certainly attack the address books of all accounts on the computer, whether they’re Administrator accounts or limited user accounts. And any program that deletes My Documents can get all the My Documents folders on the machine, guaranteed. Anyway, your antivirus software should be looking for malicious programs and protecting your entire machine. That’s simply not the job of an Administrator account. Of course, if you’re using a limited account and you bump into a virus, Trojan horse, worm, or some other form of sniveling scumware, the program can’t do as much damage. Because malware inherits your authority (and limited user accounts don’t have much authority), you may be slightly better off. Slightly. After all, you still have a virus infecting your machine.

By definition, a Virus is something which can self-replicate itself into multiple hosts. A computer virus could spread by floppy discs, USB drives, emails or any other communication protocol available which can send data from one computer to another. Viruses are usually stealthy, hidden inside other legitimate applications or documents and don't destroy data or incapacitate the affected computer immediately after infection. Instead they use that time to infect other computers around them. Trojans, on the other hand are defined as something which impersonates as something else to fool the user. The key difference between a Trojan and a Virus is that while viruses hide inside a legitimate document or application, a Trojan impersonates as a legitimate document or application itself and usually doesn't do anything useful. The second significant difference is that while most Viruses spread automatically without any human intervention, Trojans usually require human interaction to infect the computer. E-mail based Viruses which infect a user's computer only after the user opens them are actually Trojans.