memory Consumption

Dear all, I have installed Suse 9.0 in two pcs. 1. A Pentium III with 256 MB of RAM. 2. A AMD 3200 with 1024 MB of RAM. Both have the same problem. Using top can see that used memory increases by 4-20kb every 1-2 secs and free is reduced by that amount. Further buffer size increases. Eventually all physical and swap is used and if unlucky will Hung too! Has anybody came across the same problem and if so what is set so wrong? Why buffer size increases all time ? Thank You, Savvas