--Common error codes
The steps in this guided walk-through should help with all Windows Update errors and other issues—you don''t need to search for the specific error to solve it.
As an example, here are some commonly seen error codes: 
0x80240034; 0x8007000E, 0x80242006​, 0x80244018​, 0x80D02002​, 0x80246017​, 0x80240438​, 0x80070070​, 0x8007000D​, 0x80246008​, 0x80096004​, 0x80070020. 
The steps provided here should help fix any errors that come up during the Windows Update process.
How does it work?
We’ll begin by asking you questions about the Windows version you''re using and the issue you’re experiencing.
Next, we’ll take you through a series of troubleshooting steps that are specific to your situation.
At the end of each step, you’ll be asked “Did this resolve the issue?” 
If it’s resolved, select Yes, and you’re done! If it isn’t resolved, select No and continue with the guided walk-through.
From Start , search for cmd

Right-click Command Prompt from the results and choose Run as Administrator
At the Command Prompt, type the following commands one at a time. After each, press Enter. Let the command complete before typing the next command.{
	net stop bits
	net stop wuauserv
	ren %systemroot%\softwaredistribution softwaredistribution.bak
	ren %systemroot%\system32\catroot2 catroot2.bak
	net start bits
	net start wuauserv
	Close the Command Prompt window, and reboot your computer.
	Check for Windows Updates again.
}

--·清理垃圾
net stop wuauserv
rmdir  /s /q C:\Windows\SoftwareDistribution\Download\*
del /s /q C:\Windows\SoftwareDistribution\DataStore\*
net start wuauserv
--qemu-img convert
sdelete64.exe c: -z
qemu-img convert -O qcow2   op54i3win7jpx64-3xx.img  op54i3win7jpx64-3xx_.img
--win7 uefi
在用光驱安装win7时，启动时有两个光驱启动方式，一个为开头为efi的，一个则为光驱号
如果用efi开头的那个启动并安装则系统保留分区为默认efi格式，而且无法更改，导致无法更改盘符，而后无法用激活工具激活
所用解决办法就是从光驱号那个光驱启动方式启动，并格式化硬盘为NTFS格式，则安装完成后那100M的系统保留分区为NTFS格式，这样就可以添加盘符并激活了

Windows 7的100MB系统保留分区在系统下是不会自动分配盘符的，但是可以手动给它分配一个盘符，运行具有管理员权限的CMD.exe，然后输入：
diskpart
sel disk 0
list vol
sel vol 1
assign letter=R
通过这几行命令会给这个保留分区分配盘符R，你也可以通过磁盘管理工具来给它分配盘符。

--qemu の仮想マシンのイメージのディスクサイズを変更する。
サイズを拡張{
qemu-img resize  b85m-win7cnx64q35-2xxx.img  +100G
qemu-img info b85m-win7cnx64q35-2xxx.img
virsh start  b85m-win7cnx64q35-2xxx
virsh blockresize  b85m-win7cnx64q35-2xxx  /VM/b85m-win7cnx64q35-2xxx.img  300G
}

サイズを縮小{
qemu-img resize --shrink  -f qcow2 b85m-win7cnx64q35-2xxx.img -100G
qemu-img info b85m-win7cnx64q35-2xxx.img
virsh start  b85m-win7cnx64q35-2xxx
virsh blockresize  b85m-win7cnx64q35-2xxx  /VM/b85m-win7cnx64q35-2xxx.img  200G
}