Windows 7 networking issue - "Invalid Username and/or Password"

This is the third time I'm trying to make this post. This is absurd. What do you have only a minute before you get timed out? This time I saved it to notepad so I can paste it...

I just wrote out about 10 paragraphs only to have it all lost because this site had logged me out before I could submit it. Just another frustration.

Well, I'm not going to sit here and type everything out again. Took me forever. So I'm just going to sum it up.

I keep having the same issue when trying to share data on a Windows 7 network. It's beyond frustrating. In my opinion, Windows 7 network is unintuitive and broken.

Today I had to replace two computers on a clients network. It's a simple small business network where I'm just using a normal computer running Windows 7 to share some data. The problem is that sometimes, at random, a computer will not connect to the share. It will tell me that I have the wrong username and password when the share doesn't require a username or password. I made two identical computers that were set up the exact same way. The first time they both connected to the share just fine. I was shocked and happy as I almost always have the issue I'm describing.

However, I ended up having to reformat one of the machines and set it back up again. I did so the exact same way. This time it won't connect to the network share. It prompts me for a username and password and no matter what I put it will not let me connect. I have been having this issue for a long time here and there and have never been able to fix it without reformatting the machine. I have tried countless suggestions but nothing ever works. Once it does this, I have always had to reformat.

I do not understand how it could work and then a couple hours later it won't after a format. The hardware hasn't changed and the settings haven't changed. I have been through the policies, through the advanced sharing settings and the network settings and everything is identical to the machine that will connect with no problem.

How can this be? Can anyone think of a way to get this thing to connect without having to reformat it until it randomly works?

Thank you for your time.