1. Install Python 2.7
2. Install Twisted 11.0.0 for Py2.7, then Zope.Interface (a .egg file) for Py2.7: http://twistedmatrix.com/trac/wiki/Downloads
3. Untested, proposed by TeaRex: install Zope.Interface from http://www.lfd.uci.edu/~gohlke/pythonlibs
If this doesn't work, you will have to install the egg file:
to install setuptools
to download, then run ez_setup.py
4. Go to C:\Python27\Scripts
5. Run easy_install.exe zope.interface-3.6.4-py2.7-win-amd64.egg
After that, download joric's pywallet.py at https://github.com/joric/pywallet
Throw that inside C:\python27
Make a .bat file, and put:
C:\Python27\python.exe pywallet.py --dumpwallet --password=FILLYOURPASSWORD
inside. Remember to put your wallet password to replace FILLYOURPASSWORD, and add:
if your wallet.dat isn't at the regular place, add '--datadir=DATADIR ' with DATADIR at the location of wallet.dat
Copy the contents of the CMD window down to a text file. If you have ONLY received coins on a couple of address, find them and copy the data for the 'sec' column. Just make a blockchain.info wallet, and import those privatekeys to the wallet (choose Sipa wallet format or Base54, I've forgotten that). You'll see the balance there. Afterwards, just get a new wallet file by deleting the old wallet (BACKUP FIRST) and restarting the bitcoin client. Try sending test amounts of coins to it (faucet?) ,and if it works just send the coins back to it. You can also try other alternative clients like Electrum or Armory.
Your wallet should be dumped with JSON format, then you can import it to blockchain.info/wallet (easiest) or Armory and other clients.