Best way to fix the computer IP in the router

[#1]

Problem is very simple - but new to me.
If I put Wondows 7 to sleep instead of switching off it shuts down but retains the IP address.
Now if the other computer starts up first it can steal the IP address and I get an IP address conflict.
The easy way is to just give the Windows 7 computer a fixed IP address in the higher numbers however I have read that when doing thisI should restrict the router IP address range - one problem is that the Netgear standard Ip address for contacting the router is 254.
Would there be any problem in fixing the IP address as say 50 and ignoring the reast or should I go into the router and set a fixed IP address for this machine

[#2]

You could do either, or both - I think if you set a static IP in windows it'll be issued that IP each time, likewise if you set the mac address against a static IP in the router. Setting the IP as 50 should be fine.

[#3]

Reason found - just lost connectivity to the Plusnet servers so checked the router log and found that it had done a full reboot at sometime in the early morning - the times in the log are a bit mesed up but there may have been a significant delay before it managed to connect to the servers
Thu, 2009-10-29 04:11:27 - Receive NTP Reply from time-g.netgear.com
Thu, 2009-10-29 04:09:35 - Router start up
Thu, 2009-10-29 06:09:04 - Initialize LCP.
Thu, 2009-10-29 06:09:04 - LCP is allowed to come up.
Thu, 2009-10-29 06:09:15 - CHAP authentication success