Emachine El135201e does not boot 1 long and 1 short beep

be sure nothing on you keyboard or pressing any key

Yes, Michael Thomas is right. This is a POST (power-on self-test) that takes place at the beginning when you boot your computer. I think this is because the BIOS chip that came with the replaced motherboard. Take care how many beeps are and if them are short or long. Who is the BIOS manufacturer? Find the error code then go here: http://www.computerhope.com/beep.htm and determine the problem. Or search google for "post beep codes" .

The exact type of beeps matter (eg.: two long, three short). Generally, beep codes indicate something is badly wrong, often the RAM.

Well if it's 3 short beeps then its a RAM failure. If its 1 long and two short then it;s a video monitor issue. 3 long beeps is a keyboard or keyboard card error.

Here are the beep codes for common BIOS programs:

1 BeepA single beep from an AMI based BIOS means there has been a memory refresh timer error. The solution is often to replace the RAM in the computer.

A long beep from AWARD is probably memory error.

1 short beep from AWARD bios & PhoenixBIOS and most others is a positive ok signal.

Without more information, it sounds like it is a memory problem. Remove the memory and see if it will boot to the BIOS/setup screen. If so and you have multiple memory sticks, put one in and try to boot. If that fails try the other.

Hard Drive is bad and probably needs to be replaced.
Good Luck...

most likeley if you see something on the screen but it wont boot it is a mem problem, does it load bios, if so it is prob not memory

The beep codes below may help you identify the possible computer problems. However,
they are only for reference purposes. The situations might differ from case to case.
gAMI BIOS Beep Codes
*Computer gives 1 short beep when system boots successfully.
*Except for beep code 8, these codes are always fatal.
1 beep Refresh failure
2 beeps Parity error
3 beeps Base 64K memory failure
4 beeps Timer not operational
5 beeps Processor error
6 beeps 8042 - gate A20 failure
7 beeps Processor exception interrupt error
8 beeps Display memory read/write failure
9 beeps ROM checksum error
10 beeps CMOS shutdown register read/write error
11 beeps Cache memory bad
g AWARD BIOS Beep Codes
1 short: System boots successfully
2 short: CMOS setting error
1 long 1 short: DRAM or M/B error
1 long 2 short: Monitor or display card error
1 long 3 short: Keyboard error
1 long 9 short: BIOS ROM error
Continuous long beeps: DRAM error
Continuous short beeps: Power error

Using the manual for the Gigabyte GA-945P-S3 MB. Go to page 71 & you'll see bios beep codes for your board: AWARD BIOS Beep Codes 1 short: System boots successfully 2 short: CMOS setting error 1 long 1 short: DRAM or M/B error 1 long 2 short: Monitor or display card error 1 long 3 short: Keyboard error 1 long 9 short: BIOS ROM error Continuous long beeps: DRAM error Continuous short beeps: Power error As you can see there isn't a code for three short beeps. When you boot your system try to pause your boot up screen. See if the bios is reporting the correct total of memory in your system. Bios codes from the link below. http://www.computerhope.com/beep.htm#05 3 beeps for the AMI bios code reports Base 64K RAM failure. You can test your memory. Go to memtest.org Scroll down the site to just under the three screen shots. Download Memtest86+ V2.11 You have a choice in making a bootable floppy disk or a bootable CD-ROM disk. Once completed you boot your system to the testing program. Memtest will check your system memory. This should help. Thanks for using FixYa! Mike

The beep code most likely is either video card or memory.
If you have a video card or can borrow one that you know it works try it first, if that doesn't resolve your issue try the memory.
You can take the memory out and have it tested to see if it is defective.
Go to this site and get the Beep Codes, http://www.computerhope.com/beep.htm
I hope this helps.
Good Luck.