It is physically repairable but is it ecconomically repairable? As a frame only its probably worth £100-150. Factor in the cost of repair, fresh powder and decals, all the running around, cost of fuel, postage etc and it simply isn't worth it.
Now if you had sentimental attachment towards it then it would be worthwhile. But bought in 98, ridden for just two years, dumped in a damp shed for a decade, then stored under the bed for another three, my guess is that it doesn't really hold a special place in your heart.
Best choice is to hang it from the wall in the garage as a reminder of the follies of youth.