所有文件用默认的方式打开，就选择打开方式选择程序，系统提示“该文件拒绝访问”
怀疑对象：
征途旗帜木马病毒修改了注册表.
解决：从网上搜索到下面的方法，使用后问题解决
第一步：新建一个文本文件，保存为*.reg，*为随意文件名。
第二步：复制下列代码到文本文件，然后双击导入注册表。
Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\Unknown]
"AlwaysShowExt"=""
"QueryClassStore"=""
[HKEY_CLASSES_ROOT\Unknown\shell]
@="openas"
[HKEY_CLASSES_ROOT\Unknown\shell\openas]
[HKEY_CLASSES_ROOT\Unknown\shell\openas\command]
@=hex(2):25,00,53,00,79,00,73,00,74,00,65,00,6d,00,52,00,6f,00,6f,00,74,00,25,\
00,5c,00,73,00,79,00,73,00,74,00,65,00,6d,00,33,00,32,00,5c,00,72,00,75,00,\
6e,00,64,00,6c,00,6c,00,33,00,32,00,2e,00,65,00,78,00,65,00,20,00,25,00,53,\
00,79,00,73,00,74,00,65,00,6d,00,52,00,6f,00,6f,00,74,00,25,00,5c,00,73,00,\
79,00,73,00,74,00,65,00,6d,00,33,00,32,00,5c,00,73,00,68,00,65,00,6c,00,6c,\
00,33,00,32,00,2e,00,64,00,6c,00,6c,00,2c,00,4f,00,70,00,65,00,6e,00,41,00,\
73,00,5f,00,52,00,75,00,6e,00,44,00,4c,00,4c,00,20,00,25,00,31,00,00,00