Is this a safe overclock?

I just overclocked my cpu and i just want to make sure if this is safe. Im quite new to oc'ing so im only 85% sure what im doing lol. Before i overclocked to 3.6 and that seemed all fine so i bumped it up to 3.8 and i found that my system was running a bit slow. So i looked online to see why it went slow after overclocking and it said to increase the cpu voltage by 0.25 every 100mhz over the default clock and it would help. So i go into the bios and did that and it looked alittle high, so i just increased it by 0.25 to be on the safe side. And id like to just post what has changed in my bios so i can get some advise from you guys whether i should increase some stuff or decrease it.

My setup is:
Gigabyte ga-990fxa-ud3
AMD phenom ii x4 840 (propus)
8gb corsair
asus hd6950 2gb
ocz modxstream pro 700w

I have increased my cpu to 3.8ghz (238mhz)
vCore is increased by 0.25v (1.375v)
Ram is at x6.66 (1586mhz)
Northbridge is at 2142mhz

Is this a safe overclock? and would i be able to hit 4ghz, if i can how? And can you plz recommend if i should increase or decrease anything for best performance?

Thanx

edit: and its water cooled

as long as temperature below 60C under stress Prime95 ... it's very safe
u can try to 4GHz if lucky, as long as temperatures remain low and try to add one step at either FSB or votage (raise vcore till u get stable max 1.45v), try to close near NB to 2000 - 2200 and the drop ratio RAM maybe ran at 1333 . just opinion

Yeah I did a little more tweaking last night and I kicked it right up to 4.0ghz and the vcore if I can remember rightly 1.45v and my system failed to boot. Before that if I went to 3.8 and increasing the v by .25 it gave me the big fat blue screen of death when I tried to run prime95. I haven't tried running prime95 with the core raised to 1.45 but I'll try it tonight. But why would my computer fail to boot when raised to 4.0ghz? Should I lower the ram even more or increase the vcore?

edit: lol double post from ipad

Sweet thanks for the help i appreciate it

Also just one more question, if i oc my 840 to 3.8/4.0/4.1ghz with the voltage at the necessary setting, lets say 1.48/1.55/1.6 and my temp doesn't go over 30-35 degrees c while running prime-95 for about an hour, how much will this decrees the life of my cpu?

Good iv ajusted my ram settings a little above that and it seems to be working better than before. In my bios should i unlock my cpu or should it locked?

no unlock ... your CPu is 4 core and enough