I'm finally getting back into cycling heavily, Recently I've been commuting to college/work (one and the same) and its 11miles each way, 4 days a week, I've been doing it on a BD Dawes SST setup in single speed. I have been riding rain or shine [luckily I am waterproof, mostly -that's what I always tell people when I ride in the rain ]; but do give myself a break sometimes [take the train most of the way some days -on those days the ride one way is 3-4+ miles total]

This winter I plan to start commuting the whole way on the better days, and doing a partial commute on really bad days or days I want a break. The problem is, I do not want to ride a single speed road bike in the Chicago winters we have here; lucky me though as I have a K2 mountain bike [Zed 3.0 hardtail, '06 I think] that I've had and used lightly for the last 6+ years.

Unfortunately I have been really lax on maintenance and I need to readjust the derailleurs, replace the chain, maybe get a decent seat or just swap the stock one for something lying around, a new seat post [the one on there is too short], the disc brake calipers may need to be replaced as they are original [but last time I rode it they seemed just fine -famous last words?].

I would also like to replace the tires [and tubes] for something more winter cycling worthy and not worn out, it has stock WTB '2.14' tires on it but they seem to be exactly 2" wide, there is currently about .5" clearance on the sides and .75" clearance above the tires -mud flap clearance is not a problem because I have clip-on ones for the front and back that -though I am considering upgrading these as they don't cover much of the tire. At minimum I want to get a half decent studded tire set, I don't need a fancy studded tire because it will be ridden on roads that should be mostly cleared, and the rest of the time through snow on a path, and ice spots on both. I am also planning to put some packing tape or duct tape over parts of the frame then put some SOLAS tape on that to make it easy to remove if I decide to do so later. I have plenty of rear lights as well [two Radbot 1000's, an older Cateye one, and a few others]

I also have a Topeak rear rack for it and a set of Novara panniers I got when I got the bike; though I think a decent trunk bag will be better in snow and ice conditions as it won't get snow dumped on it and if I wipe out it shouldn't get smashed to the ground like panniers would.

Initial budget of $200 for upgrading/ replacing parts, If I feel like it, or if the winter decides to kick into high gear this year I will spend accordingly and get some more stuff when I need to.

The bike in question [and the light up Christmas tree that is my Dawes SST in the background]

Tire clearance:

So things I need/ want/ am considering, more or less in this order:
Brake pads, chain, tires 'n tubes, toe clips of some kind [BMX type?], seat post, trunk bag, pedals, another headlight, different rain/ mud guards, handle bar [to change things up a little]. Then some cycling clothing for the winter, jackets/ hats/ gloves and such I have covered, but I need something to cover my pants and I need to find some decent boots as I have none AFAIK.

Recommendations, additions to the list, or comments?

I can't wait to see what the bike will look like when snowed on, bring on the winter!