Problem with virus

I found this two days ago when I ran a thorough scan using AVAST (the last update distributed in July).

Win32:Trojano-872 [Trj]

My problem is that the computer freezes and it was doing the same thing several months ago - until I had to replace the disk.

The symptom is as follows.
I am running a certain program of mine for numerical analysis in VB6 environment.
When I ask the program to “solve” an easy problem with a small number of data and (as a result) it runs fast to give the answer, nothing happens.
If there are many numbers and you have to use memory and speed of execution is low then it may cause the system to freeze.
The program is OK and it does n’t happen always.
Thought it was corrected when I removed the above virus but now it did it again.

It’s a mystery - no one can find why it happens.

The antivirus does the same think (freezes system) when I try to scan the other disk - the old one with the problem. In that case maybe it is natural since the disk has a problem. But the freezing is identical (nothing works i.e. mouse, ctrl-alt-del).

Sounds more like an overheating problem to me (the freeze occurs under heavy load).
What system is it? (CPU, OS)

It’s Windows xp.
By heavy load you mean use of memory ?
It’s probably some 50,000 - 100,000 declared variables what I 'm trying to do.

As for heat we do have some of it in Athens right now (> 35 degrees) !

No, I mean heavy use of CPU - which may raise the temperature of your CPU. Especially when there’s hot around (it’s terribly hot here too, btw).
If your room has say 10 degrees more than usually, the CPU will be hotter as well - and it may cause the freezing. Don’t know how fast your CPU is, but make sure it’s cooled properly. Of course, it doesn’t have to be CPU only… fast memory modules may suffer from the same problem, high-end graphic cards as well, etc. Shortly said, cooling is very important, especially in hot wather.

If it were a software problem, simple crashing or bluescreens would be more likely; this kind of freezing (when mouse doesn’t move) sounds more like a hardware problem to me.

May be you are right.
I 'm going to talk to my technician.
When it happened before it was, infact, August last year with above average temperatures !
As a matter of fact my disk was in its last throws and I was waiting for a friend to come from abroad to help me replace it. As he delayed his arrival I did nothing and then I got hijacked also and subsequently the disk gave in and I replaced everything.
But the first symptom was this freezing again with this numerical analysis - number crunching tool thing !

Does that make you more positive it is a hardware-temperature related problem ?
Anyway I 'm not 100% sure yet.
I have another two pcs in cool environment but they are used for other purposes.

Well, it is a possibility, but it’s really hard to say for sure.
There is various temperature monitoring software available (maybe you got one with your motherboard); also, you can usually check the current temperature in your BIOS (even though this one is without the CPU load, so it may be lower than later, when you run a CPU-intensive application). So, you can check the temperature of your CPU and let us know. On the other hand, every CPU has a different “reasonable range”, so this information may not be very helpful either.
You know, this kind of “random error” problems are hard to solve…