Have a look at this page "
http://www.dschnabel.de/irdoku.htm"
The site is in german, but explains quite well the possibilities for changing the existing "irremote.ini" found in the Windows directory.
I'm using a PVR350 with another remote as the 250 but basically you can reconfigure the buttons like you want.
First of all you have to add the application "Media Center=" below the line "[Applications]"
Afterwards you could add for example the following lines I'm using :
[Media Center]
FULLSCREEN={ctrl}w
BACK={esc}
MUTE={Ctrl}m
VOLUP={ctrl}{add}
VOLDOWN={ctrl}{subtract}
CHNLUP={ctrl}n
CHNLDOWN={ctrl}l
OK={enter}
STOP={ctrl}s
PAUSE={ctrl}p
PLAY={ctrl}p
REWIND={ctrl}{left}
FASTFWD={ctrl}{right}
SKIPFWD={ctrl}n
SKIPREV={ctrl}l
BACK={esc}
MENU={menu}
FUNC={tab}
0={ctrl}{shift}0
1={ctrl}{shift}1
2={ctrl}{shift}2
3={ctrl}{shift}3
4={ctrl}{shift}4
5={ctrl}{shift}5
GRNPOWER={alt}{f4}
********************
I use the numPad of the remote to give a rating to the current song.
In fact you can control other applications or even switch between applications using for example the following commands
"GREEN={close(wintv2k.exe)}{sleep(750)}{run(C:\Progra~1\JRiver~1\MediaC~1\MediaJ~1.exe)}"
The green button on my remote closes WinTV and starts Media Center.
You have to try different settings to suite your preferences.
Some remarks at the end :
1) When finished editing the irremote.ini file you have to use the "Restart IR" command from the WinTV Start-Menu.
2) You can't use the "Write Playing" Plugin because the remote needs the name appearing in the taskbar.
3) the remote acts only for the currently active window, so you have to use the "Go" key to switch between open applications.
Good luck