Folder Access Issues

I posted this in the security forum, then realized that it may not apply to that forum, so I will try here.
Ok, I have a couple issues that I need help with.
I'm new to windows 7 Home Premium, so bear with me.
I have a toshiba laptop with windows 7 Home premium installed.* I have a wireless home network set up using a linksys router.
Problem 1.
I have a NAS (Network Drive), that is hooked up to my router, and I have several shared folders on the NAS, that require an ID/PW to access them. On my old XP laptop, I would just have to enter the ID/PW once, and would always have access to all of the folders.* With the new Windows 7 laptop, when I access the NAS via name (\\backup-drive), it asks for an ID/PW, and I enter it, and it tells me it's not valid, even though I tested it again on another machine and the ID/PW work fine.* Could my NAS be the issue?* I know I had to install a patch for Vista (wife has a vista laptop), but they don't seem to offer one for windows 7, so I'm assuming that is the issue.* Anyone know?* The NAS is a Buffalo tech Linkstation 250GB drive (HD-H250LAN-it's discontinued).
I wanted to add, that the very first time I tried to access the NAS, I did as I do on XP and typed in \\backup-drive in the "run" box, and hit enter, and it opened a window that showed all the folders, but then asked for ID/PW when I would click on any folder, and would not take the ID/PW I entered, but ever since then, I don't even get the window showing all the folders on the NAS anymore, now it just asks for an ID/PW and still won't accept what I enter.
Problem 2.
I seem to keep running into an "access denied" issue with many folders (documents and settings, application data, temporary internet files, etc).* I have admin access, and can usually play around with the permissions to get access, but then I have to do the same thing with another folder, and any sub folders.
Is there a way to change this using the security policy?* If so, where is it?* I saw another thread where someone said that it's under "control panel">"system & security">"administrative tools", but it is not in that location.
Can someone help me solve this "access denied" problem that I am getting, even though I am an administrator?
Let me know if you need any more information.

Thanks.

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