In the Windows Automated Installation Kit, you have all the tools you need to create customized maintenance operating systems.  Many people have asked how to optimize the boot time and size of these mainenance OSs.  I thought I would point out a few of these OS options with some tips:

Use the Diagnostics and Recovery Toolset bootable CD from MDOP
Usually, you'll want to use the Diagnostics and Recovery Toolset boot disk that is prebuilt and ready to go with enterprise tools such as a system sweeper that even work offline with Bitlocker.  One great part about using the pre-built recovery environment in DaRT is that you can create custom boot CDs that only include your drivers, allowing the boot time to be quicker.  You can just download and go with this option, and

Use Windows PE on a bootable disk
But if you don't own the DaRT, then you can create your own Windows PE and include your own tools that you want.  You can even create an HTA shell for a user inteface to your tools and/or scripts. All you need to do is simply create an HTA application like this sample app:

<HTML>
<HEAD>
<TITLE>HTA support is functioning</TITLE>
<HTA:APPLICATION
WINDOWSTATE="maximize"
BORDER="none"
INNERBORDER="no"
SHOWINTASKBAR="no"
SCROLL="no"
APPLICATIONNAME="HTA Verification"
NAVIGABLE="yes">
</HEAD>
<BODY BGCOLOR="FFFFFF">
<DIV STYLE="position:relative;left:90;top:140;width:80%;">
<FONT COLOR="Gray" FACE="Tahoma">
<H2>Welcome to Windows PE.</H2>
HTA support is functioning.
</FONT>
<BR><BR>
<BUTTON ACCESSKEY="C" STYLE="font-face:Tahoma;font-size:13px;"
onclick="self.close()"><U>C</U>lose</BUTTON>
</DIV>
</BODY>
</HTML>

Then copy that HTA to the windows\system32 folder of you Windows PE image and edit the winpeshl.ini file to include the following sections:

[LaunchApps]
%systemroot%\system32\mshta.exe, %systemroot%\system32\testhta.hta

Much of this is documented in the Windows Automated Installation Toolkit on MSDN in the Windows PE Walkthroughs, a few important ones are linked here:

Use Microsoft Deployment Toolkit lite-touch boot disk
When you use the Microsoft Deployment Toolkit, you are essentially customizing a version of Windows PE, adding the task sequencing engine and the user interface for all of the migration processes, such as backing up the user data and selecting an image to download over the network.  Although you could modify the built in Windows PE to have your recovery environment tools available, usually you are keeping this copy of Windows PE separate from your recovery environment.  The tools are different for each task, and you might end up with a significantly large image, which can seriously extend your boot times.

Use Windows PE as a local partition
The same techniques of creating a custom Windows PE image with your tools can be used to create a locally installed OS that is on the local hard drive of the PC, usually as a recovery environment.  Once you have your customized Windows PE image, edit the bootloader to put this option on the boot menu.  Steps three and four on this link shows you how to do this:  http://technet.microsoft.com/en-us/library/cc722114.aspx.