Hi Sorry to trouble the community, but I cannot seem to reinstall Router OS on my RB450G. I tried to follow instructions at http://wiki.mikrotik.com/wiki/Manual:Netinstall. I'm pretty familiar with IT but am not a comand line person and not a network person either.

I'm on a new HP Laptop with Widows 10 installed.
I reset my RB450G by holding down the reset button and powering on and keeping the reset button pressed for about 2 minutes
I have downloaded and installed the Netinstaller
I downloaded and decompressed routeros-mipsbe-6.38.1.npk which is the correct OS for my router
I have disabled avast antivirus on my laptop
I have set my IP Address on my Ethernet Adaptor under IPv4 to 192.168.1.1 with Subnet mask as 255.0.0.0
I used IPCONFIG to determine my Default Gateway and on my Ethernet Adaptor under IPv4 configured that as 192.168.1.1
I run Netinstaller and select the routeros-mipsbe-6.38.1.npk file
I click on NetBooting and tick the box for Boot Server Enabled client IP Address is set to 192.168.1.2
I connect Port 1 on the RB450G to my Ethernet port using a 1 meter CAT 5e cable.
I power on the router while pressing the reset button and wait at least 30 seconds.
I leave the RB450G alone and my laptop running.

Nothing happens, but after a couple of minutes the router beeps the same way it does when it is power cycled. I assume that Router OS may have been successfully installed but I don't know. The Netinstaller interface tells me nothing.

When I go to Winbox I try to log on as I did before (but with default credentials) but I cannot logon.
I try to
Connect To 4C:5E:0C:39:0A:9A (listed as one of the 2 MAC addresses on the sticker on the device, I tried the other Mac address as well).
Logon admin
Password admin

Sorry to trouble you with what may be obvious and simple for some of you, I tried my best to search the forum and to use available advice on YouTube and other sites but I cannot figure this out.

I had the Router set up by someone else who is knowledgeable but they are not available and anyway I have to figure this out so I can support my network myself. Thankfully I backed up my configuration and managed to restore from successfully recently. But today I locked myself out of my RB450G by setting the IP Address for a device on my network to the same IP as my laptop (which is the only widows device I have configured with winbox that has access to my RB450G) by accident, so I need to start with a fresh install and restore my config, I just cannot seem to get into my RB450G with a fresh install of RouterOS.

- Major snip -
But today I locked myself out of my RB450G by setting the IP Address for a device on my network to the same IP as my laptop (which is the only widows device I have configured with winbox that has access to my RB450G) by accident, so I need to start with a fresh install and restore my config, I just cannot seem to get into my RB450G with a fresh install of RouterOS.

As far as re-installing ROS I can't help you, but if your primary issue is that you can't access the router because it has the same IP as your laptop, change the IP of your laptop, and then you should be able to access the router.

I think that ip address have to be 192.168.88.1 for the router and 192.168.88.XX for the laptop

If it's in default configuration, ether1 won't work. Try connecting to ether2 on the RB450G. Do you see anything in Winbox Neighbours tab?