Why should I clean the registry most games consumers don't know what a registry is. People are not getting the point. An average consumer of video games expects to put a game into a machine that meets the required spec install it in around 30 mins and be playing it is that too much to ask for. I'm not an it tech and neither is the vast majority of the games market but since you kindly took the time to reply with something I haven't tried I will and I will get back to you thank you jimbuna

Thank you bilgerat that is probably the problem the tech guy at PC world said it would be fine and the games diagnostic program says it would be fine. Like I say I'm not an IT guy and neither is 90 percent of the video games market. As far as I was aware with the info I had the spec of my PC was more than enough. Change is needed or the PC sim will die and I will miss them.
This is Lt Scott Cooksey. Last survivor of the PC games market. Signing off.
Thanks for all your help guys but I've had enough. I'm going to stick to my Xbox.

Because Windows sometimes flubs the uninstall process and not everything uninstalls cleanly. If you are using SH3 with SH3 Commander, for example, there are links through the registry entries which let SH3 Commander work some of its magic. If those links are not cleaned up properly, you might encounter problems. The fault would be with Windows, not Silent Hunter, but it still would impact your game. Other programs, not all of them games, have the same issues.

All the SH products are complex programs. You can not compare them to Flight Sim, which provides a here-and-now environment without much complex AI interaction and with no past and future. SH has campaign layers, where historical events are simulated, a scripted environment which is much larger than the game horizon, AI which must react to the player's actions but not be so good as to overwhelm him, and the real-time simulation of the sub itself, including animations within the sub. The SH games are far more complex that an FPS. And still, the stock game - SH3 and SH4, not so much SH5 - plays OK right out of the box, without any fixes by the gamer. They are all A LOT BETTER with mods, but if you can not get them to work rock-stock, then you have done something wrong. Running SH5 in an environment which is inadequate will guarantee you a very unsatisfactory gaming experience. But that is hardly the fault of the game, or of its developers.

Already answered above...I'd suggest a free piece of software 'CCleaner'

http://www.techspot.com/downloads/132-ccleaner.html