If you're running NTFS, and you really should be on your system drive, defragmenting is really unlikely to make a performance difference.
Defraging NTFS won't make trem run faster, however depending on how fragmented your drive is, it could
greatly improve load times. Additionally, if your page file has been set to autogrow for a while, it too can become fragmented. The only way to fix that is to remove the page file, defrag as much as possible, the recreate the page file at a set size. My only thought in this is that a lot of the younger folks playing trem may have downloaded large zip files/ISOs etc, (ala pirates bay) and could have a pretty heavily fragmented drive.
WARNING if your computer has a fragmented page file, there's a good chance you need that page file. Removing it and rebooting (which will be required) may cause extremely painful slowdowns until the page file is recreated, assuming your computer successfully boots.
What may help is to check for running processes in memory using the task manager. Lots of programs leave little helpers behind that are ultimately pointless and stupid, doing little else than checking for an update once a day or less. Some of the culprits are java, adobe acrobat, adaware, some zip programs, etc. I haven't used windows in a while so I don't recall any more, though I used to run into tons of them. If your machine is squeezed for memory, the little amount freed by stopping/killing these programs may make a considerable difference. If there are many of them, the amount of memory they consume may be substantial. Running msconfig from the run dialog comes to mind. I seem to recall that as the name of the program that will simplify locating programs that are run at boot time.
For more advanced users, I'd also recommend checking your system services. Turn off and/or disable any that aren't needed. But I warn you, MS seems to intentionally obfuscates their service names and does not do a good job of defining what they do, so if you don't know what a service does don't touch it. Or at least remember the services you changed and be prepared to change them back. I've seen windows systems do strange things when seemingly (completely) unrelated services are disabled, prepare yourself to reenable them if you run into weirdness. I'm reminded of a win2000 box that failed making VPN connections when a service that appeared (by name and MS web site) to have nothing to do with VPNs, encryption, tunnels, etc was turned off.
All of this is really just an end run around the real performance enhancer, in case you are for some reason unable to do it:
The single most effective performance enhancement has always been, in my experience, to add memory. If your GPU is the issue, memory may not help, for all other things it will. Scavenge old machines, talk to friends or family, they may have an old computer sitting unused that has the same type of memory that your system uses. You'd be surprised where you can find memory if you ask around and/or keep you eyes open for it. Its not as easy as it used to be (which was VERY) as there are many different types of ram these days, its still worth it though.
