Is there a built-in windows password store?

Windows Credentials

Yes, there is a windows password store.

They are stored hashed within files in the c:WindowsSystem32Config directory. You will need the SAM and system files. However, a backup of these files may be stored in the Windows repair folder at c:WindowsRepair. SAM contains the hashed passwords, however they are encrypted using the boot key within the system file. If Windows is running and you need access to the locked files in the Config folder (for example you know the files in Repair are out of date), you can extract these files using regedit.

  C:>reg.exe save HKLMSAM sam

The operation completed successfully

  C:>reg.exe save HKLMSYSTEM sys

The operation completed successfully

An alternative is to use tools such as Pwdump which can extract the hashes stored within the SAM/system files directly without the need to use regedit or manual decryption of the SAM using the boot key. Windows passwords may also be cached in memory. Windows Credentials Editor can extract these values in plain text from the Windows Digest Authentication package.

  C:>wce -w

WCE v1.3beta (Windows Credentials Editor) - (c) 2010,2011,2012 Amplia Security - by Hernan Ochoa (hernan@ampliasecurity com)

  Use -h for help.

testMYDOMAIN:mypass1234
NETWORK SERVICEWORKGROUP:test

You will need local administrator access to do all of the above, unless you can mount the partition from another machine to directly access the files in the first case. Network Credentials Network passwords are stored inside Windows Vault/Credential Manager: