VirtualAcorn Technical support:
Problem with VirtualAcorn on Windows Vista

At VirtualAcorn we have been running various versions of Vista on machines since June 2006. This means that we have been able to document any problems and make sure that our products worked before Vista was launched.

If you do encounter any problem when running VirtualRPC on Windows Vista then the first thin to check is that User Account Control has been disabled. For further details please see the Disable User Account Control Article.

Problems with unlocking VirtualRPC

Quiting/Crashing before reaching the Registration window

A situation arose on one of our test machines where whatever was done VirtualAcorn would not run. After a good deal of investigation we discovered that this was a problem with the ntdll.dll component in Windows. If your VirtualAcorn won't start up and gives an error message check to see if the error is coming from the NTDLL.DLL component of Windows. This relates to the built in DEP (Data Execution Prevention) found in the hardware of certain processors. The problem with DEP first turned up on AMD processors running Windows XP SP2 and is documented in various places on the Internet. Recently we have had it show up on both Intel and AMD based machines.

There are two potential solutions to this problem:

Solution One
Our extensive tests show that if you repeatedly shut down (not hibernate) the machine and re-start it eventually VirtualRPC will run. This can be time consuming but is simple. In our test case it took 20 reboots before VirtualRPC started.

Solution Two
This is a quicker solution but is a little more complex and involves running VirtualRPC in "compatibility" mode. To do this right click on the VirtualRPC icon on the Windows backdrop and click on Properties. Now click on the Compatibility tab. Select the compatibility option for Windows 98/ME. Now click OK. VirtualAcorn will now run. Note that it will be running very slowly but this doesn't matter. Once VirtualRPC has entered the RISC OS desktop close it down. Now go back to the Properties window and untick the Compatibility options. You can now run VirtualRPC normally with no problems. This method seems to work as once an application has been "registered" with DEP it's not checked again as Windows decides that as it has been run before it is "safe" to allow the task to start and execute.

Once you have got VirtualRPC to run it will then continue running without the error ever showing up again.

Note that this is not a problem with VirtualAcorn products but with Vista/XP on certain hardware, many applications can be affected, including some of Microsoft's own products (Windows Explorer crashes on some machines), AVG anti-virus, Skype etc. Not all machines are affected by this problem but there does not seem to be a way of determining if the problem will occur on a particular machine until it does. The problem seems to occur more often on AMD machines than on Intel based ones.

As Intel processors currently (August 2010) offer the best performance when running VirtualAcorn we recommend that users do not purchase AMD based machines with Windows Vista at the present time and instead stick to Intel based hardware.

Quitting/crashing directly after unlocking

A situation turned up on one of our test machines where VirtualAcorn wouldn't unlock correctly. It would go through the process then crash once the licence agreement had been accepted. A bit of experimentation provided a work round:

Firstly VirtualRPC needs to be run in "compatibility" mode. To do this right click on the VirtualRPC icon on the Windows backdrop and click on Properties. Now click on the Compatibility tab. Select the compatibility option for Windows 98/ME. Now click OK. VirtualAcorn can now be unlocked as per usual. Note that it will be running very slowly but this doesn't matter. Once VirtualRPC has entered the RISC OS desktop close it down. Now go back to the Properties window and untick the Compatibility options. You can now run VirtualRPC normally with no problems.

Error messages from Windows on trying to run VRPC

"Missing" sound hardware

We have have had an interesting problem with a desktop PC that had been supplied with Vista pre-loaded - but didn't seem to have any sound hardware shown at all. Checking from the Windows device manager didn't show any sound devices. We asked the customer to check round the back of the machine and low and behold it had a full set of audio sockets. We suggested that the user tried re-installing the audio device drivers from their motherboard CD. They did this and re-booted but the sound hardware still didn't appear and VirtualAcorn still crashed out.

Further investigation revealed that the machine had no speakers connected. So what? Of course no speakers means no sound, but the hardware will still be present. Well apparently not. Vista had detected that the machine didn't have any speakers and so was disabling the sound hardware. Not just switching the volume off, or some other sensible tactic, but actually preventing the sound drivers from loading and making the hardware "vanish". The user didn't want speakers, so my only suggestion was to buy a cheap pair of headphones and plug them in. Then turn the volume down and leave the headphones hidden behind the computer on the desk.

Run as Administrator

VirtualAcorn may need to modify it's .cfg files, they can also be modified by the user to alter aspects of the program's behaviour and performance. As VirtualAcorn is located in the Program Files folder, so are its .cfg files. Windows Vista won't allow files that are stored in program files to be altered by an application. So what seems to happen is that your changes get "lost".

There are a number of issues involved here so we will try and keep things at a rather abstract level. Under Windows Vista you can arrange for a task to run with Administrator rights. Assuming that VirtualRPC is already installed there will be a shortcut icon on the Windows backdrop. Right click on this and click on Properties. Now click on the Compatibility Tab and make sure the Run this program as administrator button is ticked. Now click on OK. This will set VirtualRPC to run in Administrator mode. Note that although we have changed the properties for the shortcut on the Windows backdrop these settings apply to the VirtualRPC program itself despite the method that is used to start it.

Configuration changes being lost

A user was altering the amount of memory allocated to VirtualAcorn in the .cfg files. Saving them, then running VirtualAcorn and discovering that the changes hadn't been applied. Going back to the .cfg files showed that the changes that had been made had vanished. This was because User Account Control had not been disabled on the PC. If you have this problem then see the Disable User Account Control Article.