Small Business Network Issue

Hey guys. So here's the situation. First of all, my brother is the computer genius in the family, and he's the one that set up our father's business network. I believe it was last summer, the business switched to a new windows based version of Prophet 21 (our business software) and at the same time got a new server and re-did the whole office (7 computers plus the server computer) network. Most of the computers run different versions of windows. A few are on XP, some are on 7, and I believe one is running 8.

We went to Staples to buy a new computer for the billing clerk, because his old one was running slow and was really old. The problem is, as soon as we installed that computer (HP i think) it was CRAWLING on the internet. It would connect locally to our server and to the database just fine, but he can barely get online at all. It took 23 minutes to load gmail. Not cool. We tried having the computer looked at by a tech company near us that works on most of our stuff, and they found nothing wrong, but gave us a new tower anyway. So, with my brother not working here anymore, I've been thrown into the IT guy position haha. I took to the web to try and troubleshoot as best I could, and this is what I've come up with:
All the other computers in the office are connecting to the internet as normal, no speed decreases of note.
His "new" computer is running Windows 7 Pro, and will connect locally to our business database software just fine.
I tried checking ping times on this computer (the one directly attached to the server) to have a control value, and am getting 5-7ms pinging google.com.
Tried the same ping on the trouble computer and got 6-7ms. Then booted in safe mode with networking, and got the following ping times: 276, 346, 275, 276. Then re-booted normally and got 276, 274, 277, 286.

No other computer in the office is having this issue, and I am totally stumped as to what to do. It doesn't make any sense to me why it would have normal ping times, then crappy ones in safe mode. Did I mess up by booting it in safe mode?
Basically, we need to get this issue resolved, and I can't for the life of me figure out how to fix it. The more suggestions you guys can throw at me, the more I can try. I'm not the best with software, but I can figure it out with decent instructions, or if you guys could point me to a place where I could find them. Anything you guys give me would be awesome.

~Jake

 

Update:

Re-ran ping to google.com, times are back down below 7ms.

Ran ipconfig/release & renew, then ipconfig. Came back and said Ethernet adapter LAN is connected and showed adress, but below that had two tunnel adapters:
Tunnel adapter isatap.
Tunnel adapter LAN
both of these had a Media State of "disconnected".

Is that what my problem is? If so, what the heck is it that I should be looking for?

 

Domain or workgroup?

If domain, then check DNS and reverse DNS.

 

Other trouble shooting possibilities hardware related -
Go to Device manager and uninstall network adapter and reboot. Driver will be reinstalled. This checks for possible corruption.
Replace ethernet cable from computer to wall connection in case of damage.
Try wireless connector (USB dongle) to see if the problem is software or hardware related. If wireless works up to speed, may be a faulty wired adapter from the factory. Warranty issue.
Try computer in another wired location to see if faulty wiring in wall at original connection point.

 

Theefool-
I don't know if it's Domain or workgroup. Like I said, my knowledge level with this stuff is severely lacking. But if you tell me how to find out, I can follow directions and figure it out. And by check/reverse DNS, those are terminal commands?

LB-
Tried uninstalling network adapters and rebooting. Didn't change anything. Ping times to google steady at 7ms. He's trying the wireless right now. We've tried different cables, and different connections on the router, those don't change anything.

What little troubleshooting knowledge i retained from my time in the navy tells me that that means the problem is has something to do with the computer itself. The Problem is, we tried it on his other computer (this one has windows 8) and it has the same problem. So, could we really have two computers- one running windows 7, one on 8- with the exact same problem? I feel like maybe there's some network or firewall setting, or maybe some program that would be commonly installed on both of them, that might be causing the trouble. The most ridiculous thing is that (both) his computers can connect just fine to our local server that has our business software & database, but they load internet pages slower than the speed of smell. We need him to be able to e-mail customers and vendors, so we really need internet connectivity on his computer (either one!) asap.

Thanks for the suggestions guys, please, keep them coming so I can figure this out

 

hello, I will try to help but my english isn't that good so I am sorry about that.
so you saying that you got network, all work and only the new server can't connect the internet?

and you said you ping from the server to google and you got normal ping?

first, you know what install on this server and what his roles? DBA?microsoft SMB? exchange?
secend, if its microsoft servers, its 2003?2008? meby 2012 ?

now, to check if this server member in domain right click on the pc icon and go into properties.
then you got "change properties" or something like that (I just dont have english on my pc right now).
now there is a button to change the pc name. when you click on it you will see in the buttom if the server member in workgroup or domain.

I dont think its DNS problem. because its resolve GOOGLE name without any problems at all. most of the servers got high protect on defulte setting that block alot of sites and URL with the explore.

In my opinion, if you dont NEED to get out to the internet with the server you shouldn't do it and even block it.
I mean if its for check email and etc, there is normal clients for it and the Core servers are for critical roles inside the lane. Its to risky to get to the WAN with them.

but if you need the internet for exchange or something and you got only 1 server you have no choice...

good luck,
Or