Why does it keep restarting?

Well heres whats up. First off i installed an old 80gig HD as a backup for more space. Ever since i installed that HD everytime i try encode 2 or more .ogm files with the program alltoavi OR try to play a game it gets either about half way through the encoding process or about half way through encoding and the system just restarts itself and comes up with 1 of 2 error msg's. The first one that happens is once it restarts it comes up with a screen saying a disk read error occured press Ctrl+alt+del to restart youre computer and the second one being that once the computer restarts it starts beeping and shows me a warning saying i didnt connect my power cord to my 9800AIW pro. Now my computer never had ANY of these problems before i added this harddrive and even since ive taken it out it still has these problems. Ive ran the Symantec anti virus that came with my system and housecall. The symantec scan came up with nothing and the housecall scan showed some adware but that was it so i just cant think of what the heck could be causing these problems if ANYONE has ANYTHING they could help me with id LOVE to hear it........sorry about the length of that post im already late for work so i just typed THANKS PPL!!

 

What about the temperature? Could be getting hot & shutting down.

Is everything OK in the device manager? What's the operating system?

Install anything besides the new drive? Hardware? Software?

 

Adding to Hipster: Did you check to make sure that you didn't loosen any cables when you installed/uninstalled the HDD? This isn't too likely but if you have a spare IDE cable lying around, try using that one, could be that the cable was damaged during the installation. Does your PSU have enough watts to support the two HDD's? It is possible that you overloaded the PSU after the installation. So, following in Hipsters question: what are all your system specs?

 

Well my System is a Cicero"futureshop" brand AMD Athlong 64 3000+, 512 mbram , 160 gig HD, the one that is currently unplugged is an old 80, 9800pro AIW video card, Soundblasterlive 24 bit Soundcard, dvd burner. Thats all i can think of if you guys need any more info im not sure how to get it so ill need someone to tell me a program or something that can find out anything else THANKS ALOT PPL