How do I know if my computer has malfunctioned virus?

Hi,
I use Lenovo desktop, recently I update all the software but after that my computer work slow and it will give me errors like application problems, out-of-memory errors when I start my computer. For solving this problem I installed all the application again but after that I am not going to update the application, but then also I get this error when I start my computer. I think this is virus problem but How do I know if my computer has malfunctioned virus, can anyone give me suggestion how I solved this problem.

Yes I think this is a virus problem I am not sure for finding if this is a virus problem then check following conditions, these are the problems occurs when you have virus in your computer.

• Windows will not start properly; when it is start up it will give errors.
• Some time windows will not start because certain critical system files are missing.
• Sometime it goes hang during the startup.
• If its start then it will work slowly, take long time to start up.
• Give you out of memory errors, even though the PC has plenty of RAM.
• Task manager shows that an unknown process is consuming a high percentage of the CPU time.
• Applications are not able to start properly.
• Windows continuously reboot.

I tell you how your computer infected by virus.

• Download the files from the unknown zone of internet or download the attachment from the email which has odd attachment, such as the appearance of odd dialog boxes or a sudden degradation in system performance.
• Download some attachment which has double extension such as .jpg.vbs.
• Antivirus software will not properly install on the computer.
• Use cd,dvd or pen drives or any other memory storage without virus scanning.

Take care of your computer from the virus for that you have to installed latest antivirus with all latest updates and use windows Firewall protection, I think this solution will help you to solve your problem.

I have some information about the virus; following are the some infection type and how they infect your computer.
• Trojan horse: this speeding itself via e-mail, or deleting or damaging files. This program delivers a harmful effect.
• Worm: These viruses are make copies of it and spread over the network.
• @m: this virus will attaches itself to email and downloaded with the attachment.
• @mm: it’s a user's address book virus it will automatically send itself to multiple addresses from address book.

I tell you the solution when your antivirus will not able remove the virus from computer that time you have to recover your operating system, before recovering you have to take backup of your data from your computer. And if your operating system is not able to recover then you have to format your computer, and I think solution will help you to solve your problem.