In fact, when I went to find it through the directory,
and clicked on it just to highlight it, it made the hard drive light go solid
blue. When I tried to restart my computer, everything was going really slowly
and took about 30 minutes to finally shut down and restart. Is this a virus?
can I get rid of it? (I also have v4.0, so do I even need v3.5?)
I have a Inspiron 1525 with Windows Vista Home Premium
What kind of scan? File itself is a legitimate part of .net Framework 3.5 SP1 - I have it on my XP PC as well. Could be a false positive or a red herring - e.g., the actual problem is somewhere else in the system, but is tangled up with .net Framework in some way.
VirusTotal doesn't pick up any "hits" on that file as being malware (EDIT - fixed link, earlier one was for a different file).
The .net Frameworks aren't really cumulative. If you have a program that requires a particular version (e.g., 3.5) there's no guarantee it will work with .net 4.0. Same with earlier versions (1.1, 2.0, 3.0, etc.).