It should not ask you to sign in again (unless you specifically signed out at some time, if you did, don't sign out)
You are allowed to have your Lightroom serial number activated on two computers simultaneously, so if it is the same computer, it will not count as the second activation.
The sign in request also states that this is a trial version and I will have to license it after 30 days. I already licensed it a few days before. The installation was from a dvd. Everything was working fine until Win 8 updated itself... The pc crashjed on boot up several times after that and now runs slow. From your reply am I right to assume if I license it again it will not act as a second activation. If I decide to buy a new computer and install LR how do I tell Adobe that I am not using LR on a second computer so I don't use up my second activation. Thank you for your help.
If you Sign Out of LR that Deactivates the install on that computer. Which would set your Activation's back to Zero.
In your case since a Win 8/8.1 update It seems something got FUBARed on your system and no telling if Signing back in would count as a second activation.
If your computer is running slow I would first try to fix that. This wouldn't be the first time Microsoft has released buggy updates. That is one reason to turn off the Auto Update system in Windows and do them manually when you have free time and can look at what exactly is being updated.
Okay, let's clear things up. You are NOT limited to two activations. NOT limited to two activations.
You are limited to two activations simultaneously. That is different.
To indicate to Adobe that you are no longer using a particular activation, you sign out of the software.
How do I sign out of the software if its not functioning?
Your original question was "Installed lightroom perpetual license; a few days later it asks me to sign in again . if i do this will it count as the second installation"
If it is asking you to sign in again then at some point you signed out or the program lost the reference that you had signed in.
Now you are asking how to sign out if the program doesn't function. If the program doesn't function then how is it asking you to sign in?
You need to be more descriptive in what the program is and isn't doing. If it starts and asks you to sign in on the exact same computer you originally installed it on then signing in a second time shouldn't count to more than one activation. Adobe records some type of computer ID code it is installed on. So if you haven't changed any hardware in the computer signing out and back in 100 times on the same computer would still only count as one activation.
So what exactly is happening and if the program isn't functioning how do you know it wants you to sign in again.