让我提前感谢您阅读并试图帮助我。谢谢！抱歉编辑得很糟糕，还不得不更改一些链接，因为我的信誉不佳 :)
我的问题是这样的：打开更新软件中心时出现一个错误窗口，提示：“在修复包目录之前，无法安装或删除项目......”我单击修复但失败了。
运行 sudo apt-get update 失败这是错误报告：
"W: Failed to fetch archive.ubuntu.com/ubuntu/dists/precise/Release Unable to find expected entry 'restricted/source/Sources' in Release file (Wrong sources.list entry or malformed file)
W: Failed to fetch bzip2:/var/lib/apt/lists/partial/us.archive.ubuntu.com_ubuntu_dists_precise-updates_main_binary-i386_Packages Hash Sum mismatch
E: Some index files failed to download. They have been ignored, or old ones used instead."
source.list的内容：
# deb cdrom:[Lubuntu 12.04 _Precise Pangolin_ - Release i386 (20120423)]/ precise main multiverse restricted universe
# See help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.
deb us.archive.ubuntu.com/ubuntu/ precise main restricted
deb-src us.archive.ubuntu.com/ubuntu/ precise main restricted
## Major bug fix updates produced after the final release of the
## distribution.
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team. Also, please note that software in universe WILL NOT receive any
## review or updates from the Ubuntu security team.
deb us.archive.ubuntu.com/ubuntu/ precise universe
deb-src us.archive.ubuntu.com/ubuntu/ precise universe
## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
## team, and may not be under a free licence. Please satisfy yourself as to
## your rights to use the software. Also, please note that software in
## multiverse WILL NOT receive any review or updates from the Ubuntu
## security team.
deb us.archive.ubuntu.com/ubuntu/ precise multiverse
deb-src us.archive.ubuntu.com/ubuntu/ precise multiverse
## N.B. software from this repository may not have been tested as
## extensively as that contained in the main release, although it includes
## newer versions of some applications which may provide useful features.
## Also, please note that software in backports WILL NOT receive any review
## or updates from the Ubuntu security team.
## Uncomment the following two lines to add software from Canonical's
## 'partner' repository.
## This software is not part of Ubuntu, but is offered by Canonical and the
## respective vendors as a service to Ubuntu users.
# deb archive.canonical.com/ubuntu precise partner
# deb-src archive.canonical.com/ubuntu precise partner
## This software is not part of Ubuntu, but is offered by third-party
## developers who want to ship their latest software.
deb extras.ubuntu.com/ubuntu precise main
deb us.archive.ubuntu.com/ubuntu/ precise-updates restricted main multiverse universe
deb-src extras.ubuntu.com/ubuntu precise main"
我尝试过：阅读其他类似的答案并按照他们的建议进行操作：
1. 更改我使用的服务器
2.
sudo apt-get autoclean
sudo apt-get autoremove
sudo apt-get -f install
3. 以下操作也不起作用：
cd /var/lib/apt
sudo mv lists lists.old
sudo mkdir -p lists/partial
帮助我 askubuntu，你是我唯一的希望！再次感谢