I wrote a solution to this problem two days ago:

How to use p2pool with an accompanying standalone bitcoind

(since the windows gui version of bitcoin 0.5.1 crashes frequently when used with p2pool)

Assumptions:

OS: Windows 7

Bitcoin: Latest stable release installed and working - http://sourceforge.net/projects/bitcoin/files/Bitcoin/bitcoin-0.5.1/bitcoin-0.5.1-win32-setup.exe/download

p2pool: you'll be slightly off the beaten path with this configuration as you're specifying the bitcoin address to send generated bitcoins and not using the second bitcoin processes wallet

1. Download latest current p2pool code and extract to "%programfiles%\p2pool" - https://github.com/forrestv/p2pool/zipball/master

2. Download and install latest Python 2.7 (if you get 64bit, you'll need 64bit versions of the packages below) - http://www.python.org/download/

3. Download and install python extension package twisted - http://www.lfd.uci.edu/~gohlke/pythonlibs/#twisted

4. Download and install python extension package zope.interface - http://www.lfd.uci.edu/~gohlke/pythonlibs/#zope.interface

5. Download and install python extension package pil - http://www.lfd.uci.edu/~gohlke/pythonlibs/#pil

6. Download and install python extension package pygame - http://www.lfd.uci.edu/~gohlke/pythonlibs/#pil

7. Open your Bitcoin GUI client if it is not running and generate a new address, take note of the generated address and close your Bitcoin GUI client

8. Edit your existing "%appdata%\bitcoin\bitcoin.conf" and unless you know what you're doing, change what ever is there to this and if the file does not exist - create it:

   logtimestamps=1
   

9. Create the folder "%programfiles%\p2pool\bitcoind-data"

10. Create "%programfiles%\p2pool\bitcoind-data\bitcoin.conf" with your favorite text editor and populate it with this:

    server=1
    logtimestamps=1
    port=18333
    rpcport=18332
    rpcuser=bitcoinusername
    rpcpassword=bitcoinpassword
    rpcallowip=*
    

11. Take note of the folder name of the latest current p2pool code - it is in "%programfiles%\p2pool"

12. Create "%programfiles%\p2pool\p2pool.cmd" with your favorite text editor and populate it with this:

    @echo off
    title p2pool
    echo.
    echo running p2pool ...
    echo.
    C:\Python27\python.exe "%programfiles%\p2pool\folder-name-of-the-latest-current-p2pool-code\run_p2pool.py" --net bitcoin --address yourbitcoinaddresshere --bitcoind-address 127.0.0.1 --bitcoind-rpc-port 18332 --bitcoind-p2p-port 18333 bitcoinusername bitcoinpassword
    echo.
    echo p2pool stopped.
    echo.
    pause
    

13. eg.

    @echo off
    title p2pool
    echo.
    echo running p2pool ...
    echo.
    C:\Python27\python.exe "%programfiles%\p2pool\forrestv-p2pool-4f6c2e2\run_p2pool.py" --net bitcoin --address 12uN6G1uAtn7G29qfTdLD9des4y63Whr61 --bitcoind-address 127.0.0.1 --bitcoind-rpc-port 18332 --bitcoind-p2p-port 18333 bitcoinusername bitcoinpassword
    echo.
    echo p2pool stopped.
    echo.
    pause
    

14. Create "%programfiles%\p2pool\bitcoind.cmd" with your favorite text editor and populate it with this:

    @echo off
    title bitcoind
    echo.
    if exist "%programfiles%\bitcoin\daemon\bitcoind.exe" (set programfilesx86=0)
    if exist "%programfiles(x86)%\bitcoin\daemon\bitcoind.exe" (set programfilesx86=1)
    if %programfilesx86%==0 (goto :programfiles)
    if %programfilesx86%==1 (goto :programfilesx86)
    echo ERROR! bitcoind.exe not found in either "%programfiles%\bitcoin\daemon\" or "%programfiles(x86)%\bitcoin\daemon\" - giving up!
    echo.
    pause
    goto:eof
    :programfiles
    echo running bitcoind.exe from "%programfiles%\Bitcoin\daemon\" ...
    "%programfiles%\Bitcoin\daemon\bitcoind.exe" -datadir="%programfiles%\p2pool\bitcoind-data"
    echo.
    echo bitcoind stopped.
    echo.
    pause
    goto:eof
    :programfilesx86
    echo running bitcoind.exe from "%programfiles(x86)%\Bitcoin\daemon\" ...
    "%programfiles(x86)%\Bitcoin\daemon\bitcoind.exe" -datadir="%programfiles%\p2pool\bitcoind-data"
    echo.
    echo bitcoind stopped.
    echo.
    pause
    

15. List item

16. Copy blk*.dat from %appdata%\bitcoin to %programfiles%\p2pool\bitcoind-data

    Run "%programfiles%\p2pool\bitcoind.cmd"
    Run "%programfiles%\p2pool\p2pool.cmd"
    

You should now be able to mine on your machine to 127.0.0.1:9332 or to your machines IP on port 9332 on your LAN :)