Sign of a Virus Infected PC and How to Fix it

from your question, what are the kinds of computer viruses, here is the detailed explanation:

Computer viruses are generally defined as a program inputted into a computer that allows replication of the program installed. As it replicates, the program intentionally infects the computer, typically without even the user knowing about the damage being done. A virus, unlike worms or Trojan horses, needs an aid to transfer them to computers. Viruses usually take a large amount of computer memory, resulting into system crashes. Viruses are categorized to several parts based on its features.
Macro Viruses A macro virus, often scripted into common application programs such as Word or Excel, is spread by infecting documents. Macro viruses are known to be platform-independent since the virus itself are written in language of the application and not the operating system. When the application is running, this allows the macro virus to spread amongst the operating systems. There are thousands of macro viruses that exists, and each are considered major threats. Examples of these viruses are: Melissa.A and Bablas. pc.
Network Viruses Network viruses rapidly spreads through a Local Network Area ( LAN), and sometimes throughout the internet. Generally, network viruses multiply through shared resources, i.e., shared drives and folders. When the virus infects a computer, it searches through the network to attack its new potential prey. When the virus finishes infecting that computer, it moves on to the next and the cycle repeats itself. The most dangerous network viruses are Nimda and SQLSlammer.
Logic Bombs The logic bomb virus is a piece of code that are inputted into a software system. When a certain and specific condition is met, such as clicking on an internet browser or opening a particular file, the logic bomb virus is set off. Many programmers set the malicious virus off during days such as April Fools Day or Friday the 13th. When the virus is activated, then various activities will take place. For example, files are permanently deleted.
Companion Viruses Companion viruses takes advantage of MS- DOS. This virus creates a new file with typically the .COM extensions, but sometimes the .EXD extension as well. When a user manually types in a program they desire without adding .EXE or any other specific extention, DOS will make the assumption that the user want the file with the extension that comes first in alphabetical order, and thus running the virus. The companion virus is rare among Windows XP computers as this particular operating system does not use the MS-DOS.
Boot Sector Viruses Boot sector viruses generally hide in the boot sector, either in the bootable disk or the hard drive. Unlike most viruses, this virus does not harm the files in the hard disk, but harm the hard disk itself. Boot sector viruses are uncommon at this day and age because these viruses are spread rapidly by floppy disks and not on CD-ROMs.
Multipartite Viruses Multipartite viruses are spreaded through infected media and usually hides in the memory. Gradually, the virus moves to the boot sector of the hard drive and infects executable files on the hard drive and later across the computer system

The Virtumonde or Vundo Trojan is a Trojan Horse Virus that is one of the most popular and deadly viruses infecting computers these days. It is a widely-spread trojan that shows a large amount of unsolicited pop-up advertisements and also silently downloads harmful files from the internet.

The virus is responsible for decreasing the amount of virtual memory available on your computer and it can considerably slow down the performance of your PC. That is not to mention all the other dangerous forms of activity it can spread across your Computer, such as installing more viruses adware, malware, spyware, and also Stealing private information such as passwords and credit card numbers.

Now If you are looking for a way to completely remove the Virtumonde virus from your computer then you've come to the right place. This page is dedicated to help you remove the virtumonde virus. It will run you through exactly what a Vundo Trojan is, where it comes from, how it effects your computer and how to completely remove it from your computer for good

Viruses are programs that get into your computer environment without your knowledge and then use your computer to connect to other computers and install a copy of themselves in those computers adn thereby spread. Virus programs are usually not content to just spread. After replicating, a virus program may do a silly prank, harm to your computer by corrupting files or even destroy its ability to serve you. Virus programs may also give a hacker a back door into you computer and thereby allow the hacker to use your computer to clog other sites or to steal your identity. If you think you have one disconnect from the web immmediately and remove it with anti virus pattern recognition tools. Avoid the free ones. Use a major product that large companies depend on. An anti virus program can be a virus itself.