hi all new to the forum here, so hello to everyone. i apologize in advance for the long-winded nature of this post, but i wanted to include as many details as possible. i am writing because i have a potentially very big problem, caused by a possibly quite ill-advised attempt at a do-it-yourself replacement of both the hard drive and CD-R/DVD optical drive in my 'desk-lamp' model G4 iMac, which i've had for several years. it's done an admirably reliable job for me over those years, but in recent months has gotten painfully slow at times and has frozen up on me at start-up on one or two occasions, at the grey screen with the apple icon with the loading icon underneath, which after some research i learned was a sign that the hard drive might be crapping out. so, since i wanted to upgrade the original 40gb HD anyway, i figured i may as well replace the hard drive entirely, with a new 160gb Seagate model i purchased from a (fairly reputable, i think) online merchant. i also replaced the original CD-R/DVD drive with a new Pioneer CD-R/DVD-R drive. as far as i know, both of these drives are brand new, as in never used and not refurbished. then, using guides i found online, i proceeded to attempt the surgery, which went well as far as i could tell, insofar as there were no huge discharges of static electricity (i was wearing a grounding bracelet) and i didn't outright snap anything in half. i reconnected the optical and hard drives in the same configuration as their predecessors, which i believe had the optical drive as 'master' and the hard drive as 'slave' (though i'm not 100% sure, since i'm not entirely clear on how to tell which is which), and made sure to keep track of all the wires i disconnected so that i could reconnect them at the end. however, there is a connecting piece at the right side of the base that makes it rather difficult to separate the bottom part (which houses the motherboard) from the top part (or dome) that contains the HD and optical drive. i mention this because i'm not entirely sure i was able to get this to properly reconnect when i screwed the bottom back on, though i tried my damnedest (and i'm thinking that maybe i wouldn't be able to screw it back on if it didn't reconnect?), and i'm thinking this might be a source of the trouble. anyway, the end result is that my iMac now will turn on when i press the power button, and make the nice, soothing start-up sound, before it proceeds to one of two screens, depending on what button(s) i press on the keyboard during start-up: * if i do not press any keys, it goes to the flashing question mark screen; * if i hold down the 'alt' key during start-up, it goes to a grey screen that has two buttons in the middle of it: the one on the left has a circular arrow suggesting it causes a re-start (and indeed, when i do click on it, the little ticking watch icon appears, so it seems as though it's re-starting, or at least mulling something over), and the button on the right has a straight arrow pointing to the right, which seems like it's inviting me to some wondrous next screen but has absolutely no effect when i click on it. here's the most troubling bit: i have tried re-setting the PRAM by holding down option+control+P+R right after start-up but before the grey screen, with no effect (goes straight to flashing '?' screen). i have also tried holding down the mouse button during start-up, in an attempt to get the CD tray to open, with no effect (again, flashing '?' and the tray stays closed). through random experimentation i have found that almost any key i hold down during start-up gets me the flashing '?' screen, with the exception of the 'alt' key as mentioned above. one exception is that when i hold down the 'T' key, i get a start-up sound but no screen at all, and eventually the computer shuts back down by itself. obviously, my mouse (which i have connected to the USB port on my keyboard which is in turn connected to the PC) is working, so that i can move around the cursor on the circular arrow/straight arrow alt-induced screen and press either of the two buttons with the above-mentioned (non-)effects. as endlessly fun as that is, i would prefer a little bit more functionality from my computer, and so i was hoping somebody here would be able to help me. did i kill my mac? please help!!!