Software for noise testing

One of my sites seems to suffering from exsessive noise on the physical network. Some machines can't be seen on the network and I'm convinced its down to noisy lines. I've looked at the connections etc but can see no obvious damage or other evidenceof dodgy cabling. At my last job I had a DataComm LANman tester. Unfortunatly I don't have it now and my employer wont buy me one. Is there any software around that can perform these types of test from a pc? I don't really need any real fancy stuff just a simple noise to strength ratio, cable length, and crosstalk type tests would be fine.
A sofware tester would suit me beter than a hardware tester because I could run it remotly and I wouldn't have to travel to the site.