Some application or background process is holding (not releasing memory well!) or the time and the applications running or specific applications are retaining RAM and possibly have a higher priority
--you could try renice every so oftenhttp://linux.about.com/library/cmd/blcmdl8_renice.htm
and see if you still get the slowed response to your particular set of activities (application that are running or backgrounded!)
If you can, you could also try nice to manage the priorty of the process/application you need to have such a priorityhttps://en.wikipedia.org/wiki/Nice_%28Unix%29
For interest, you could have a look at the kernel scheduler, but Linux desktops today use a pre-emptive scheduler which improves desktop OS responses (foreground usually)https://en.wikipedia.org/wiki/Linux_kernelA T61 is an older notebook, I would probably ask first: how much RAM is installedhttp://www.cnet.com/laptops/lenovo-thin ... 42903.html
--I see the max RAM is 4GB, not that much for a 64bit OS version, more RAM really helps Linux a lot in terms of performance
--you might get better performance using a 32bit OS install with PAE extension, if you want to partition the RAM (and assuming it is at MAX 4GB) to get the most space for the user applications..
Also check the SWAP space being used, or use top or htop to check: if you have plenty of RAM free, you won't have any swap space being used..http://linux.about.com/od/commands/l/blcmdl1_top.htmhttp://thegeekylinux.blogspot.ca/2011/0 ... nitor.html
--maybe some more data can be shown, why it may be considered better?