Dual monitors, extended desktop, window smaller on second screen?

[SOLVED] I solved problem myself and wanted to post answer, because could not find it on the internet.

How to fix this: Adjust resolutions and use scaling. Set the resolution on second monitor lower than native (maximum supported) resolution and scale (stretch) the pixture to full screen of second monitor. This trick will stretch the window larger and it will be the same size as on the primary monitor.

1) The initial setup
- Monitor#1 = primary: 24'' 16:9 1920x1080 left side.
- Monitor#2 = secondary: 17'' 4:5 1024x1280 (vertical = rotated 90deg clockwise), right side.
- GPU: geforce 9800gtx+ (dual DVI-D single band cables), latest drivers.
- OS: windows XP, 8 (7 not tested, but should work, because works in win8).



The AFTER setup
- Monitor#1 = primary: 24'' 16:9 1920x1080 left side.
- Monitor#2 = secondary: 17'' 4:5 974x1218, picture stretched to fullscren (vertical = rotated 90deg clockwise), right side.



2)Set scaling for secondary monitor.
- Go to: Control Panel / Nvidia Control center / Display / Adjust desktop size and position.
- Select secondary monitor / Select tab SCALING / Select: Full-screen.
- [Perform scaling on] I left it on ''Display'' to reduce the workload of GPU.
- Click OK.
- Make sure that [display resizing] in SIZE tab is turned off (empty/ unchecked box).

3) Set custom resolution for secondary monitor by using graphic card's software
STEP1)
Go to: Control Panel / Nvidia Control center / Display / Change resolution. Select secondary monitor /

STEP2)
- Create custom resolution.
Select: Customize.../ Create custom resolution. Type in values [Horizontal pixels] and [Vertical pixels]. Press TEST/OK. In popup window 'keep changes' press OK.
- Note: the lower the height (less vertical pixels) the more my window gets stretched (window becomes larger)
- Then apply custom resolution:
Win8/7: control panel/ display/ adjust resolution/
WinXP: right-click desktop/ properties/ settings/
Click on secondary monitor / select your custom resolution / press OK/ in popup window 'keep changes' press OK.

- Use the resolution calculator to maintain aspect ratio (keep right proportions of window).
http://andrew.hedges.name/experiments/aspect_ratio/
- W1: native width of secondary monitor (mine was 1024) do not change
- H1: native height of secondary monitor (mine was 1280) do not change
- W2: calculated horizontal pixels
- H1: type in vertical pixels (in first try I typed 1250)
- ''Round results to the nearest whole number'' box is ticked/ enabled
- Reduce vertical pixels by small amount.(I did 30 pixels less in first try. 30 less again in 2nd try and 2pix less in final adjustment).

STEP3)
- Preview. Place any window across two monitors (left side of window on primary and right side on secondary).
- Align (move up/down) your sreens so that the top border of the picture-window is aligned (top border meet perfectly) in both monitors.
- Check. the bottom border of the window. If bottom border is aligned perfectly on both monitors - then you have finished fixing the problem. If bottom border does not match, then repeat STEP2 and STEP3 until window is the same size on both monitors.