Microsoft is currently investigating the issue. Good news though for users who have been experiencing the black screen of death after a Windows 7 update. Security company Prevx have released a fix for the issue. They do state that it will fix the most common cause for the issue which means that it will most likely fix the problem for most users but not for all.

Here are the instructions courtesy of Windows 7 News:

To fix the Black Screen of Death Windows 7 issue:

1. Restart your PC
2. Logon and wait for the black screen to appear
3. Make sure your PC should be able to connect to the internet (black screen does not appear to affect this)
4. Press the CTRL, ALT and DEL keys simultaneously
5. When prompted, Click Start Task Manager
6. In Task Manager Click on the Application Tab
7. Next Click New Task
8. Now enter the command: ”C:\Program Files\Internet Explorer\iexplore.exe” “http://info.prevx.com/download.asp?GRAB=BLACKSCREENFIX”

Note this command assumes that you are using internet explorer as your browser, if not substitute your browser path and file details for those of iexplore.exe or use the Browser option of Task manager to locate it.
9. Click OK and your browser should start up and begin the download process
10. When prompted for the download Click run, the black screen fix program will download and run to automatically fix the issue.
11. Now restart your PC and the black screen problem will hopefully be gone.

The Prevx blog goes into more detail of the causes of the black screen of death:

By the way – the cause of this recent crop of Black Screen appears to be a change in the Windows Operating Systems lock down of registry keys. This change has the effect of invalidating several key registry entries if they are updated without consideration of the new ACL rules being applied. For reference the rule change does not appear to have been publicised adequately, if at all, with the recent Windows updates.

In researching this issue we have identified at least 10 different scenarios which will trigger the same black screen conditions. These appear to have been around for years now. But our advice is try our tool first. If it works great. If it doesn’t you are no worse off.

Users who are not able to fix the issue with this procedure might have to wait for an official fix issued by Microsoft.

Windows 7 will not assign a drive letter to the Windows Vista partition by default. Some say this is on purpose while others think that it is a bug. There is however an easy fix to access the data on the Vista drive in Windows 7.

Press [Windows], enter [diskmgmt.msc] and hit [enter] to open the Disk Management interface in Windows 7. You should see all the hard drives and partitions of the computer system. The partition containing the Windows Vista system should be without drive letter.

Right-click on the partition in the lower half of the screen and select Change Drive Letter And Path. Now click the Add button and assign a drive letter to the partition. The Windows Vista partition will now be visible in Windows 7. (via Dual Boot Partition not Showing in Windows 7)

A DVD drive not showing up in Windows 7 can have various reasons. One of the more common ones is if Windows 7 64-bit is installed on the computer. The 64-bit edition of Windows 7 verifies the digital signature of hardware drivers. If a driver cannot be verified it will be shown with a yellow exclamation mark in the device manager.

A quick workaround is to press F8 during boot to turn off digital signing. A permanent solution would be to disable the check of digital signatures completely:

1. Press Windows R, type regedit and press enter.

2. Open the Registry key

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E965-E325-11CE-BFC1-08002BE10318}

3. In the right pane, right-click UpperFilters, and then click Delete.

4. Click Yes to confirm the removal of the UpperFilters registry entry.

5. In the right pane, right-click LowerFilters, and then click Delete.

6. Click Yes to confirm the removal of the LowerFilters registry entry.

7. Exit Registry Editor, and then restart the computer.

via Windows 7 Not Recognizing DVD Drive

You can find more tips and help in our Windows 7 Forum.