For Windows 95, you need:
A 386 or higher processor
4MB RAM
At last 85MB of HDD, more is recommended
Recommended:
A 486/DX 66MHZ
8MB RAM
120MB HDD
For Windows 98:
A 486/DX CPU or higher
16MB RAM
255-355MB HDD minimum
Recommended:
At least a Pentium CPU
32MB RAM
450MB HDD is recommended for optimal settings