What is the closest thing to grep that comes standard on a Windows install?

The findstr command is what you're looking for. It's a little different than grep, but you can do some of the same things.

    C:\Working>findstr /?
    Searches for strings in files.

    FINDSTR [/B] [/E] [/L] [/R] [/S] [/I] [/X] [/V] [/N] [/M] [/O] [/P] [/F:file]
            [/C:string] [/G:file] [/D:dir list] [/A:color attributes] [/OFF[LINE]]
            strings [[drive:][path]filename[ ...]]

      /B         Matches pattern if at the beginning of a line.
      /E         Matches pattern if at the end of a line.
      /L         Uses search strings literally.
      /R         Uses search strings as regular expressions.
      /S         Searches for matching files in the current directory and all
                 subdirectories.
      /I         Specifies that the search is not to be case-sensitive.
      /X         Prints lines that match exactly.
      /V         Prints only lines that do not contain a match.
      /N         Prints the line number before each line that matches.
      /M         Prints only the filename if a file contains a match.
      /O         Prints character offset before each matching line.
      /P         Skip files with non-printable characters.
      /OFF[LINE] Do not skip files with offline attribute set.
      /A:attr    Specifies color attribute with two hex digits. See "color /?"
      /F:file    Reads file list from the specified file(/ stands for console).
      /C:string  Uses specified string as a literal search string.
      /G:file    Gets search strings from the specified file(/ stands for console).
      /D:dir     Search a semicolon delimited list of directories
      strings    Text to be searched for.
      [drive:][path]filename
                 Specifies a file or files to search.

    Use spaces to separate multiple search strings unless the argument is prefixed
    with /C.  For example, 'FINDSTR "hello there" x.y' searches for "hello" or
    "there" in file x.y.  'FINDSTR /C:"hello there" x.y' searches for
    "hello there" in file x.y.

    Regular expression quick reference:
      .        Wildcard: any character
      *        Repeat: zero or more occurrences of previous character or class
      ^        Line position: beginning of line
      $        Line position: end of line
      [class]  Character class: any one character in set
      [^class] Inverse class: any one character not in set
      [x-y]    Range: any characters within the specified range
      \x       Escape: literal use of metacharacter x
      \    Word position: end of word

    For full information on FINDSTR regular expressions refer to the online Command
    Reference.

findstr:

dsquery * | findstr "asdf"

dsquery * | find "asdf"