installing dvd-rom drive

[Brian Mc]

i already have a possible solution, but would like a second opinion before i get home and try this. here is the situation:

First, I have a HP Pavilion 7935, 256 sdram, Cd-RW...
My computer has been working fine since i bought it (a week ago) i decided to take my dvd-rom drive out of my old gateway computer (pioneer dvd-144) and add it to this one.. so i install it boot up the computer and everything is fine, it wont play dvds because i dont have a compatible decoder for windows XP but thats OK! it will read cd-roms fine and ill find a decoder in just a jiffy. BUT THEN... i turn off my computer and go to bed , i wake up and turn it on and i get this error message that says "cmos checksum bad - loaded defualts" press f1 to enter setup F2 to continue, if you choose to continue then you get an error "operating system cannot be found".
i turn it back off, open it up and disconnect my dvd-rom player completely then turn it on... It runs just perfectly.. heres how i installed the dvd-rom, please correct me.
My cd-rw which came from the factory is master, halfway down the ide cord is another connector, SLAVE, i connected the slave to the dvd-rom and changed the jumpers on the back of the dvd-rom to slave.
plugged in the power cord, and booted up. like i said, it read cd-roms just fine, it was listed in the device manager properly.. what did i do wrong? do i have to set it up in cmos first? how do i even get to cmos, i went into the bios and didnt see cmos listed anywhere. any help is greatly appreciated, im not an expert by ANY means

[Oceanis]

OK a few tips. I don't know what a Pavilion looks like so this is generic.
1. Check if the CDRW is actually set to master or if its set to Cable Select. If the latter, set the jumper to master.
2. Check in the BIOS (which is the CMOS) that both drives are set to AUTO (detect).
3. Check in Windows that the drive letters are set correctly (in Administrative Tools, Computer Management, Disk Management).
4. I heard a story (but not sure if this is true) that some HP machines have power supplies that are too low spec (too low wattage). Adding any additional equipment to those could cause funny things to happen.
Hope this helps - good luck