"So, I dl'd sarge and the install went fine. Now after a couple of weeks my system is totally unstable."
Probably the product of a bad installation.
"Once I tried to boot and there were vertical green lines on the screen during the BIOS messages and the system couldn't find the drives; I went into the BIOS and turned on SMART and changed the boot order (two things that weren't causing problems before) and then it booted fine."
Eventually, when you know how to do a correct installation, this will disappear; switch to the Debian forum in this site, where help is more available by Debian users.
Basically, answer the easy questions, like language, keyboard, at the beginning, take the default partioning, skip Dselect, at the end, install the x-window-system, locales, vim, icewm, icewm-themes, type startx and once inside the X, you can install anything with apt-get.
Check this thread:
Debian Configuration Post-Install
http://www.linuxquestions.org/questi...hreadid=224547
"The other day it froze with no kb or mouse response and the screen had some checkering blended into the normal display."
What kernel?