|"What are valid timing values to use?"|
Anything a bit more than G Skil specifies.
" Can I simply increase each number by 1 (to 10-10-10-25) or is there a need to take more care?"
Sure, try that.
Increasing the timing numbers can't do any harm, and it's extremely hard to tell the difference the higher (slower) settings make.
E.g. The first timing number is the CAS rating - that only comes into effect when the ram is first accessed, not while it continues to be accessed.
Decreasing the timing numbers to Lower (lower = faster) than the manufacturer specifies can certainly cause ram errors.
I usually use the Microsoft memory diagnostics.
There was one oddball PC133 256mb? Kingston module I had ( Kingston doesn't list it ) that tested fine when by itself, and tested fine when other modules were installed along with it, yet when it was installed along with other modules, the combo produced all sorts of errors in Windows - the other modules had no problem in Windows when that one oddball module was not installed.
I also had one Infineon DDR400 ? 256mb module that tested fine when by itself, but memory errors were produced when it was installed with any of the other various DDR modules I had on hand - all of them use standard ram voltages - yet the other modules tested fine when that Infineon module was not installed. I finally got rid of it last week when I found it worked fine in combo with a 500mb module on a computer I was working on.
It should not matter at all what SATA settings you use in the bios - that should have no effect on whether you get errors in Windows.
"An addendum to my problem is that often times the system will not boot when there is a USB hard drive plugged in."
Strange things can happen if the external hard drive can't get enough current from the USB port it's plugged into, etc.
Troubleshooting USB device problems including for flash drives, external drives, memory cards.
See Response 1:
Check that out first.
Rarely, not all the ports on the back of a desktop case may be able to supply 500ma each.
If you have a desktop computer, Note that I answered a Topic on this site recently where a guy had an external drive, which does require the full 500ma, connected to a port on the back of a desktop case - it would not work properly when a webcam was in the port next to it, but it worked fine when the webcam was unplugged. Ports on the back of a desktop case often have two ports connected to the same USB controller module that are ports one above the other - you could try connecting the cable to one of those and leaving the other un-used.
In two recent posts I've answered, the problem was with the USB cable they used between the external drive and the computer - it was indequate. For one of the two, he was trying to boot from aUSB optical drive and an operating system CD or DVD and the bios would stall forever.
By the way, you can't boot an existing Windows 2000 and up operating system installation from an external hard drive because of Microsoft defaults - but you do get an error message.