您只需要执行where语句

| where mountId != "D:"

因此在您的查询中，它将是

InsightsMetrics
  | where Name == "FreeSpaceMB"
  | extend Tags = parse_json(Tags)
  | extend mountId = tostring(Tags["vm.azm.ms/mountId"])
          ,diskSizeMB = toreal(Tags["vm.azm.ms/diskSizeMB"])
  | where mountId != "D:"
  | project-rename FreeSpaceMB = Val
  | summarize arg_max(TimeGenerated, diskSizeMB, FreeSpaceMB) by Computer, mountId
           ,FreeSpacePercentage = round(FreeSpaceMB / diskSizeMB * 100, 1)
  | extend diskSizeGB = round(diskSizeMB / 1024, 1)
          ,FreeSpaceGB = round(FreeSpaceMB / 1024, 1)
  | project TimeGenerated, Computer, mountId, diskSizeGB, FreeSpaceGB, FreeSpacePercentage
  | order by Computer asc, mountId asc

如果要从查询中排除多个驱动器，可以使用！in运算符，如下所示

InsightsMetrics
  | where Name == "FreeSpaceMB"
  | extend Tags = parse_json(Tags)
  | extend mountId = tostring(Tags["vm.azm.ms/mountId"])
          ,diskSizeMB = toreal(Tags["vm.azm.ms/diskSizeMB"])
  | where mountId !in ("D:", "E:")
  | project-rename FreeSpaceMB = Val
  | summarize arg_max(TimeGenerated, diskSizeMB, FreeSpaceMB) by Computer, mountId
           ,FreeSpacePercentage = round(FreeSpaceMB / diskSizeMB * 100, 1)
  | extend diskSizeGB = round(diskSizeMB / 1024, 1)
          ,FreeSpaceGB = round(FreeSpaceMB / 1024, 1)
  | project TimeGenerated, Computer, mountId, diskSizeGB, FreeSpaceGB, FreeSpacePercentage
  | order by Computer asc, mountId asc