求助單身老貓,, 桌麵看不見start and desk top icon again

my computer has issues. when turn on, desk top icons and start on left corner are dispear.but wall paper picture still show on back ground. use Control+Alt+Delte , Task Manager pop out.I have to use it to run the computer. I use F8 to use "last safe setup", but it does not work. my computer has Trojans and other virus, it is difficult to clear all the virus.
單身老貓replay:
under task manager
New Task
-> REGEDIT under regedit
-> Hkey_Local Machine ->Software
-> Microsof ->Windows NT -> Current Version
->Winlogon ->Shell
(MAke Sure) you have "explorer.exe"
如果沒有,手動加入,然後 restart 係統.

I can see Explorer.exe on the Shell.
if I just type explorer.exe or explorer on the Task Manager/File/new task,it show: Windows can not find 'explorer', make sure you typed the name correctly.
單身老貓,is there any other way to check the explorer or run explorer.exe?
Thank you