NoJabba, is this game for PC? (wondering as I only recently started to play some of the WarHammer games on PC, Dawn Of War & its add-ons)
as to not being able to change the graphics even after reinstalls... its possible whats happened is The game made a separate folder to save games & user defined settings too... so when you uninstall it may not be getting deleted, when you reinstall the game is automatically redirected to that folder location, finds settings & loads them.
(recently had another game I haven't played in a year do the same thing, Test Drive Unlimited, found out after installing again, it loaded my old games, configs etc etc, from last year sometime, after I removed it while having some issues & to clear up some drive space)
chances are this is what is happening with that issue, if you can find the location it saves that data too, & delete it after uninstalling, the next time you reinstall, in theory, that should reset default graphics settings... in theory, unless for some reason its something embedded in the windows registry (if this is on PC), though I don't think it would be that, but you never know these days...
recently I've been having problems with Dawn Of War not running due to the crap Securom software not working right with my DVD Burner, however Winter Assault also doesn't want to run right... when I install Dark Crusade (the standalone add-on), it runs fine, & can access all of DOW & WA units etc in Multiplayer, but I'm deprived for the single player games in the first too... sucks... had a similar issue lately with Sid Meier's RailRoads! with Securom, however installing on my other PC with the considerably older DVDROM, it runs fine...
anyways, back to your issues, try that try uninstalling the game & deleting data from any folder that would be saving your personal settings for the game, usually these folders are found in your My Documents Folder somewhere... otherwise, sometimes the games directory it installed to, wasn't entirely deleted, as it contains your personal settings, basically delete any subfolders in the main directory (or the entire directory for the game), & reinstall, one of these two methods should fix that issue... should