I recently purchased a computer from eBay. The machine has MSI P4M890 motherboard, Intel Core 2 Duo 1.86 GHz processor, 2 GB RAM, 250 GB hard drive, and NVIDIA 7100 GS graphics card. The computer worked perfectly for the first week, but then the rear USB and PS/2 ports stopped working. Externally powered devices still work on these ports (such as printers and the ADSL modem) but self-powered devices do not work (such as keyboards, mice, and flash drives). This means I must use the front USB ports for the mouse and keyboard, significantly reducing the number of available USB ports on the computer. The computer has an AMI BIOS and, in case this provides a clue, the computer beeps twice during booting. I attempted to reseat the RAM, but this did not resolve the problem. The computer is running Windows XP.

The big clue in your question is that the computer has an AMI BIOS and beeps twice during the power on self test (POST). The POST is a basic test of the system run every time the computer is started to verify all the hardware components are working correctly. When you hear abnormal beeps during the POST this indicates there is a POST beep code. Obviously the beeps by themselves are not particularly useful, so we need to find a reference to the beep codes to determine what they mean. Searching the internet I found the MSI troubleshooting website (support.msi-computer.nl/trouble/index.html) which contains a list of POST beep codes. Scroll to the “No Post ” Diagnostic codes? section. While this implies that the computer will not even POST (i.e. will not reach or complete the POST upon boot up) we can still use the beep code references to determine what they mean. Under the “AMI Beep Code” you will find a list of the beeps plus their meaning. In your situation, we are most interested in the 2 short beep code. This apparently means the computer has detected a “parity circuit failure”. This is all well and good, but what exactly does a “parity circuit failure” mean? Parity checking is a simple method of checking whether there are any errors or corruption within the data stored in the system memory. This is quite a complex topic and if you are interested in going into this in some depth then you may be interested in the following article: www.pcguide.com/ref/ram/err_Checking.htm .

For our immediate purposes the two beeps may indicate a problem with the memory or a problem with the motherboard. Since the computer is working fine apart from the rear USB ports, the problem is less likely to do with RAM. Generally if you experience a RAM problem many other things will also commence to go wrong on the computer, such as files becoming corrupt or Windows not booting correctly. To be sure, you may wish to run a memory test on the computer. One of the best memory test applications is Memtest86+ (www.memtest.org). This is a free, open source memory test application. The software works by booting Memtest86+ from a CD or floppy disk, and then runs the memory test without loading into any operating systems on the computer itself. This ensures the most reliable memory test is performed. Download a pre-compiled version of Memtest86+ from the website and then copy this onto a CD or a floppy disk. If you intend to use a bootable CD, you will need to download the ISO image (which is a single file, containing all the Memtest86+ files) and then burn the ISO onto a CD. If you don’t have a utility capable of burning ISO images, you can download the free ISO Recorder utility from isorecorder.alexfeinman.com/isorecorder.htm. Once the ISO has been burned, restart the computer with the CD in the drive and the computer should boot from the CD and the Memtest86+ scan will commence. Be aware, Memtest86+ will never stop ? it will keep scanning forever and ever. So, once you have done one or two passes of the scan you will need to simply restart the computer (using CTRL-ALT-DEL) or power-off the machine to stop the scan. If the memory scan brings up a large number of errors, you may have faulty RAM in the computer. In this case, you should contact the vendor to check whether your computer is still under warranty. Be aware, Memtest86+ may produce one or two memory errors. If this occurs, this is normal ? you should only be concerned about large numbers of errors.

The more likely scenario is that no memory errors are reported. In this case, your motherboard may be faulty. In this case, there is little you can do to test the exact cause of the problem. Instead, you should contact the vendor to enquire about warranty replacement. Since you purchased the computer off eBay, you may have limited success through this avenue. Should this be the case, another alternative is to check directly with the motherboard manufacturer (MSI) whether the motherboard itself is still under warranty. You may need to check the serial number on the motherboard so this can be supplied to the manufacturer for verification purposes.