Install BG2. Start BG2-Config.exe once. Save config.
Disable Windows' UAC (run msconfig.exe, tools, UAC start)
Execute BG2Fixpack.exe and point it to where you installed BG2. Fixpack is extracted and should start setup-bg2fixpack.exe in a DOS-command windows. If not execute manually. type in the options when asked.
Same for widescreen mod. Widescreen mod asks you for screen resolution.
Do not install english fixpack if you install bg2 fixpack.
Do not run config again. if you have to config again, modify your baldur.ini manually via a texteditor.