Starting Without Explorer.exe, Have To Run Manually From Start Menu

vista starting without explorer.exe, so have to run explorer.exe manually from the task manager to get start menu and everything running normally.... I am not sure of the right category, because this may be is related to virus, driver and system restore issues, please move in the right section, following is the system configuration and the history: also sorry for the long message, but I am really stuck here and if you could spare some time to look into this issue, I tried to provide as much history and details on the issue not just to help you understand my problem but also as a warning for other users who may run into this issue in the future.. it may be a known issue and I just happen to run into it still I would like to provide details and history of what happened, if you help me I will be in your dept for sure!! and you may ask my help anytime if you need something System configuration: my friend has a toshiba satellite latop, with vista premuim. it can preloaded on the laptop. I am not sure of the exact system model and processor but if it's relevant I can provide that info, but I suspect there is some ASUS components/drivers in the system, later I will explain why I think so, as I said I can provide system model or CPU or hardisk space but at this point I feel it's not relivant, cause it's an issue with explorer.exe right now but if you think it's required I will ask for that info, please understand I am giving support over seas from this user but we are in touch via msn and phone so if you want any additional info, even screen shots I will try to provide. History: the Problem started when she called me, and showed me a screen shot of AVG anti-virus free edition trying to remove some virususes off her computer. she said the virus came from a USB driver she borrowed from a friend. and AVG was complaining that it is not able to remove the virus because she has to buy the full AVG version. this sounded wierd, I tried to verify she is using the free AVG but I am not sure, so I ask her to uninstall AVG and try another anti-virus, first thing came to mind is avast, so I asked her to install the latest free version I think it's 4.8, but it turns out it's not compatabile with vista or her system and after some searching on the net I discover a known issue with avast/vista conflicting with some asus drivers and I suspect it is the same case, because she is also like the others reported, getting a blank screen and not able to logon. but before uninstalling avast from safe mode, I tried another suggestion ( I was not aware that avast was responsible at that point in time yet ) so I suggested she try last known good configuration. did that, but still she got blank screen again ( because avast was still there ) so I suggested she go to safe mode and try to uninstall avast ( this is after I found the issue with avast conflicing with asus drivers on some machines with vista ), after going into safe mode, she gets a view of her documents and no start button, after some questions on the phone I figured out that explorer.exe is not running, so asked her to try to run explorer.exe from the task manager, when she did that she got the start button, and was able to goto control panel and uninstall avast and then she rebooted vista. after reboot she was able to go into vista, but explorer.exe again won't run, unless she goto task manager and run it manualy everytime she reboots. I thought I'd do some research why is explorer.exe not running when the system is restarting, I thought maybe I could add it to the system startup or something, but not sure where would be the best place do to that, msconfig? or startup folder for that user? if someone can give me some advice that would be great. she already backed up her files now and ready for a re-format but I am really embarased would like to find a solution to this problem anyway, as now she think I might be an idiot for my poor selection of antivurs software, It's strange I never heard of this compatability issues and I installed avast on vista on other toshiba latops and many systems and I never had this issue ever, I suggested she try another anti-virus but she is afraid now and wants to re-format... and take her time which I understand, but in the mean time I want to try and fix this explorer.exe not runing.