Seriously off topic Major electrical Help needed!

"The power window switch which operates the rear passenger side window died so we replaced that and now the entire electrical system has gone haywire!"

It's possible the rear passenger side window went short and took out the Switch.

"The dash lights are stuck permanently on and none of the windows on the passenger side are working at all."

It's possible that a Fuse, Switch (Electronic type) or Circuit Breaker shorted on after you fitted the new Switch because of the extra short Current.

Box of red heads

I cant help with your specific problem but my wife has an e53 x5 which went into limp mode about 2 months ago, I had my mechanic hook it up to his scan tool with no luck, I then took it to the bmw dealer who also couldn't diagnose the problem on their scan tool so I had to leave it with them to sus it out. It turned out to be the abs control module, was quoted 2k plus from bmw but I found a direct replacement from a company in the states for $550 delivered. I had it within 4 days of ordering with a weekend and public holiday in that period. My point is if you need parts to fix a problem shop around to save some bux. I can give you the company name in the us if you need it.

Firstly thanks guys for the fast responses I really do appreciate it.
I'll pull the door trim off the rear and try to find any shorts ect to see if this is contributing to the problem. We've checked the Fuses and relays and the appear to be all good (plus the drivers side windows are all working) I have no idea where to look for circuit breakers or if they have them for the dash lights but I'm thinking I'll head to the wreckers tomorrow and see if i can swap the headlight switch with a known working one to see if this fixes the dash light issue.
I know what you mean obsessed about the rediculous prices for BMW parts, the old man needed a water pump for his bmw, in Australia they wanted something like $400, so he ended up getting one from the uk for $160 delivered.

if it dosent have solid chrome bumpers its a POS full stop,,oh and if it needs scan tools that dont show a fault either that just proves the point,but im happy you got a result from the old holden site,,dont forget to tell your beemer mates!

Im with you all the way on that Dave! Anything without a chrome bumper isn't worth wasting your time with. I'm very happy with the response I always get from you oldholdeners (even on unrelated things) you's are a great bunch!
Thank again everyone

check around the wire harness where the door wires come out of the b pillar, but check all of them. another thing to be aware of, is sometimes we found during production runs, some things differed before and after what is called "break points" in production of a certain model(all manufacturers do this) Lets say they may have stopped production for a week or two, for plant maintainence etc, so they improve some things by changing them during these times. it may be the wrong switch, or its also possible it could be a south african , british or oceana model that has been imported privately. I have seen good men go insane from these sort of things. Check all earthing points too. Good luck.