>>>I think some virus or Trojan got into my computer and now I only see one drive C: whereas before I had drivers D: and E:. The drive C: only shows very little space left. When I run the Windows Security Essentials it says that it cannot clean the computer and recommends downloading the Standard System Sweeper from some site. Does this sound as legitimate?
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>>Hey I didn't take the time to read all the responses to this post - were you able to recover your system?
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>Yes I did. The solution came with Kaspersky 10 Boot Clean up CD. I downloaded ISO and burned it to a CD. Then started the PC from this CD. It almost immediately found Rootkit.Boot.Pihar C and disinfected it. So far so good.
>Thank you for your help.

Kaspersky 10 Boot Clean up CD - sounds like I should put that in my "I might need this" collection. Glad you got it going again :)