The computer does not recognize flash drives and is

One or more of the hints below will probably sort out most USB problems with most USB portable / external hard drives and OTHER devices (though not always)

A few things to check but assumes USB and Windows for other interfaces / operating systems (mac/ Linux) similar steps may be adapted to suit.

1. Ensure it is connected directly to the computer to a USB 2.0 port not a USB 1.0 port as this can have effects on performance and reliability

2. Use only the cables that came with it NOT one that fits that may have been lying around or is longer. Not all USB cables are equal even though they should be)

3. Do not connect through an external USB HUB unless that hub is USB 2.0 AND has its own power supply.

4. Use ONLY the power supply that came with it if it has an external power supply Don’t use any other unless you know it has both the same voltage and current rating e.g. 12V 500mA anything rated below that would not work properly.

5. Always use the same port for connecting your devices. Some devices do not like being switched about. If switched they may want to install software / drivers again. This can be especially true if you move a HUB to another port

6. For FLASH DRIVES you should ensure that the device is set for "quick removal" using the drive control panel properties or use the USB "Safely Remove Hardware" option. If you dont do this there is a very strong chance that any files you transfer may not be there when you plug into another computer.
7. It is possible to remove drives from the enclosures in most cases and connect directly inside a PC to fully check it.
You should also do this to cheack the drives connections are not bad inside the enclosure.
8. If none of the above steps help look at updating the drivers from the manufacturers web site in the support section.

9. If you checked and fixed anything there and still have issues then check your hardware from CONTROL PANEL / SYSTEM / HARDWARE.
Any exclamation marks by hardware need fixing before you investigate any further
SPECIAL NOTES
USB flash drives can fail for no apparent reason.
Sandisk Cruzers are especially bad for this.

USB hard drives should be treated with extreme care.
This is a real hard drive ! and knocks and bumps can quite literally kill them.

Note that if you hear a drive clicking or pinging this could be the worst thing you would hear.
Known as "The Click Of Death"

First thought - Malware. Malware has a tendency to disable such things as flash drives and viruses especially can slow down your computer immensely. Head over to http://www.malwarebytes.org/ and download the free MBAM program on the left side, make sure it is updated once installed, and run a full scan. Tell it to fix/remove all issues and reboot if prompted. This will rid you of the vast majority of existent malware.

Hi, the computer just has humans require a program that allows it to recognize interact with the flash drive just like the guides we hire when we go for euro trip. the program here is the driver which recognises the USB. Please check with the drivers for the e-machine pc's in the below link
http://www.emachines.com/support/product_support.html
Hope this helps

Either you need to reinstall USB drivers so that the ports work or you are plugging flash drive into a port that isn't wired.

I've had a similar problem before and the issue could be a BIOS setting. Reboot and hit F2 or the key that gets you into the BIOS settings and check the USB settings. If legacy USB is enabled, disable it, and try again. You may have to try a couple of different settings before you get it. Good luck!