virus scan courtesy of Housecall:
http://housecall.trendmicro.com/housecall/start_corp.asp
try it in Safe Mode with Networking.
I am running Windows XP Pro on a Compaq Presario with 512 GBs bla bla bla.
The other day I clicked on word and it asked me to put the install CD in the Rom Drive. fixed that.
Then I clicked on Quicken to do my bills and it was gone no where to be found. Could not fix it the back up was on the hard drive.
Then went to run ad-aware as well as spybot, both were gone. all of these were on the desktop but missing some types of files (exe)
I also ran Windows update and the only critical update I could get failed. I have since ran it again with success.
When I clicked on Norton I found that the firewall's Intrusion Detection was turned off and it would not let me turn it on. I ran an update and it was turned back on.
I am not sure if maybe there is some new type of Virus going around or what I called Symantec and they had me run checks on there web page but found nothing not sure what to do at this point now that everything seems to be running fine.

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