I know, this has been covered thousands of times, but I can't seem to figure out what I'm doing wrong. I have a 2001 Giant Boulder SE that has a Tourney front derailleur and Altus rear derailleur. I test rode the bike after having it put up for a few years and noticed it would not shift to the largest cog in back or the smallest in front. As far as I can tell nothing is bent. I looked up a few different procedures, all of which seem to be geared toward road bikes, and followed them exactly. Now the bike won't shift at all. Is the procedure for adjusting the derailleurs different on a mountain bike?
The front derailleur, a Shimano Tourney, doesn't seem to want to push the chain onto the smallest cog at all, it appears to be dead straight and I checked with a penny so the height is correct but it doesn't seem to have enough room to push it all the way down.
The rear derailleur, a Shimano Altus, has the same issue except replace smallest with largest and it simply doesn't want to move there at all. I also cannot find a "B" screw to adjust, does the Altus not have one? Can't find any schematics of it online.
Any guidance would be greatly appreciated!

If you can't get the excellent walk-throughs available at the permanently linked Park Tool and Sheldonbrown.com sites to work for you I don't understand what you hope to gain from a "personal" briefing. No one here is likely to put the effort in into posting as many, and as clear pics as are available there.
Don't worry about the B-screw. On the overall scale of things, it's rarely that important.
And yeah, adjustment is very much the same for MTBs and road bikes. Only immediate exceptions I can think of are the rare low-normal MTB derailers and some "historic" designs.
The thing that bugs me is that bikes rarely go out of whack like that from merely sitting around, and it sounds like your limit screws are off.
If you insist on a personalized instruction, start by unclamping the shifter cables. Get the rear wheel off the ground. Turn crank slowly, push derailer sideways with your hand. See if the chain can reach all sprockets/chainrings.
If they can't, find and adjust the limit screws until they can. Then, feed out all cable from the shifters, reattach the derailers, tune with barrel adjusters, ride.

Thanks for the replies, they were kinder than I expected. I didn't know if there was a specific guide for mountain bike derailleurs. I just went out and worked on it again completely redoing the low and high limits and was able to get it shifting. Apparently last night I was not connecting the cable properly as I am able to shift again. I must have had it in the wrong gear on the shift lever when I was connecting it. Now I look like an idiot. I did get it to shift into all gears on the front and rear, however after adjusting the rear the derailleur rides directly on the largest cog when it's in that gear. That's where the B-screw comes into play, correct?

I went over the schematics on the shimano site for the rear derailleur but my 2001 model does not have a B-screw where the B-screw is supposed to be on the schematics. I can only assume that it's not adjustable and it relies on the spring that may be aging and no longer keeping it in proper position? It seems to be a lower end derailleur one step above the Tourney so if it continues giving me trouble I will have to step up to a Delore or something along those lines since those seem to be compatible with the shifter that's on the bike already and actually have a b-screw.