I have a couple of questions which have been vexing me ever since I was handed the job of upgrading Lotus Notes Clients - versions 7 and 8, at my workplace. The questions are as follows:
What would be the best possible approach - upgrade or a clean install, for client versions 7 or 8.
What is the expected duration of a clean install of version 8.5.1 on a PC powered with Dual Core processor, 1 GB DDR2 RAM and Windows XP SP2 OS.
Many thanks in advance.
Subject: Different Major versions (7.0.x/8.0.x vs. 8.5.x) → uninstall/install, 8.5.x ->8.5.y → upgrade
Other benefits:Only when doing a uninstall/install cycle, you are able to change from Single user to Multi-user installations.
One can’t upgrade and add components at the same time
etc…
While uninstalling a classic client is pretty fast, uninstalling Notes 8.x Standard needs round about 20 Minutes on current HW, take another 15-20 Min for the installation of 8.5.x
Subject: Notes client Install Experience
This is only kind of an answer to the install time, but it might help you get some bounds and make a better estimate of the install time. Having installed Notes R8.x on lots of different machines, the most limiting factor that I have seen thus far is the drive access, not the processor or RAM. There is a ton of disk access going on and a slow or very full drive can make the install process painful.
Typically, on a modern machine with a decent single drive, install times are about 10 minutes from a local install executable. However, just last week, I waited 1.5 hours for an install to complete and I could hear the drive thrashing horribly the entire time.
Subject: Installation or upgrade, to Lotus Notes 8.5.1.
That was about the same kind of experience that I have had over the past few days. On most of the PCs that I have been installing version 8.5.1, installation times have varied between 40 minutes to a full 2 hours.
Do please let me know, in your opinion what would be the best course of action in cases where Notes Client versions 8 are already installed - upgrade or a clean install.
As far as version 7 is concerned, I have had absolutely no success in upgrading it to 8.5.1. In each such case, I have had to uninstall the existing version before proceeding to do a fresh install of 8.5.1. Am I missing something?
Many thanks in advance.
Subject: More Experiences
I have had no problem upgrading R8.0.x to R8.5.x. At least, if there are issues, I haven’t seen them yet 
And the same is true for R7 to R8.x. On the client side, I haven’t seen any issues. What kind of an error message are you getting when you try to install R8.x over R7?
The times you quote for upgrades are definitely on the high side and I would suspect that you are seeing it for the same reason I did, but that is an assumption.
Subject: Link to installation guide.
I found this link of immense source of information.
http://www-10.lotus.com/ldd/dominowiki.nsf/dx/Notes_Client_Deployment